[Smartswitch] Add timeout for dhclient on DPU

[gpunathilell]

Why I did it

This dhclient call was added so that the 202505 image which does not have cid set to mac and 202506 which has explicit set for CID to mac has compatibility (DHCP server will only provide lease to same CIDs, but this WA which was added uses dhclient instead of systemd-networkd - and has no CID in the request)
The fix itself is present so that dhclient request does not take too long, since we have direct connectivity between DPU and switch, the request should finish within 5 seconds, unblocking all other systemd services and other daemons

Work item tracking

• Microsoft ADO (number only):

How I did it

Add timeout of 5 seconds

How to verify it

Verified after upgrade from 202505 to 202506 image to confirm that there are no issues:

INFO  EVAL_RESULT Expression sonic:dpu3 evaluated to 1
INFO  DHCP4_LEASE_ADVERT [hwtype=1 b0:cf:0e:0f:09:fb], cid=[no info], tid=0x4b4a4a15: lease 169.254.200.4 will be advertised
INFO  EVAL_RESULT Expression sonic:dpu3 evaluated to 1
INFO  DHCP4_LEASE_ALLOC [hwtype=1 b0:cf:0e:0f:09:fb], cid=[no info], tid=0x4b4a4a15: lease 169.254.200.4 has been allocated for 3600 seconds
INFO  EVAL_RESULT Expression sonic:dpu3 evaluated to 1
INFO  DHCP4_LEASE_ADVERT [hwtype=1 b0:cf:0e:0f:09:fb], cid=[01:b0:cf:0e:0f:09:fb], tid=0x15a9cda0: lease 169.254.200.4 will be advertised
INFO  EVAL_RESULT Expression sonic:dpu3 evaluated to 1
INFO  DHCP4_LEASE_ALLOC [hwtype=1 b0:cf:0e:0f:09:fb], cid=[01:b0:cf:0e:0f:09:fb], tid=0x15a9cda0: lease 169.254.200.4 has been allocated for 3600 seconds
INFO  EVAL_RESULT Expression sonic:dpu0 evaluated to 1
INFO  DHCP4_LEASE_ADVERT [hwtype=1 b0:cf:0e:0f:09:e3], cid=[no info], tid=0x9591f87a: lease 169.254.200.1 will be advertised
INFO  EVAL_RESULT Expression sonic:dpu0 evaluated to 1
INFO  DHCP4_LEASE_ALLOC [hwtype=1 b0:cf:0e:0f:09:e3], cid=[no info], tid=0x9591f87a: lease 169.254.200.1 has been allocated for 3600 seconds
INFO  EVAL_RESULT Expression sonic:dpu0 evaluated to 1
INFO  DHCP4_LEASE_ADVERT [hwtype=1 b0:cf:0e:0f:09:e3], cid=[01:b0:cf:0e:0f:09:e3], tid=0xcefbec15: lease 169.254.200.1 will be advertised
INFO  EVAL_RESULT Expression sonic:dpu0 evaluated to 1
INFO  DHCP4_LEASE_ALLOC [hwtype=1 b0:cf:0e:0f:09:e3], cid=[01:b0:cf:0e:0f:09:e3], tid=0xcefbec15: lease 169.254.200.1 has been allocated for 3600 seconds
INFO  EVAL_RESULT Expression sonic:dpu1 evaluated to 1
INFO  DHCP4_LEASE_ADVERT [hwtype=1 b0:cf:0e:0f:09:eb], cid=[no info], tid=0xa196a3f: lease 169.254.200.2 will be advertised
INFO  EVAL_RESULT Expression sonic:dpu1 evaluated to 1
INFO  DHCP4_LEASE_ALLOC [hwtype=1 b0:cf:0e:0f:09:eb], cid=[no info], tid=0xa196a3f: lease 169.254.200.2 has been allocated for 3600 seconds
INFO  EVAL_RESULT Expression sonic:dpu1 evaluated to 1
INFO  DHCP4_LEASE_ADVERT [hwtype=1 b0:cf:0e:0f:09:eb], cid=[01:b0:cf:0e:0f:09:eb], tid=0xe56f68a3: lease 169.254.200.2 will be advertised
INFO  EVAL_RESULT Expression sonic:dpu1 evaluated to 1
INFO  DHCP4_LEASE_ALLOC [hwtype=1 b0:cf:0e:0f:09:eb], cid=[01:b0:cf:0e:0f:09:eb], tid=0xe56f68a3: lease 169.254.200.2 has been allocated for 3600 seconds
INFO  EVAL_RESULT Expression sonic:dpu2 evaluated to 1
INFO  DHCP4_LEASE_ADVERT [hwtype=1 b0:cf:0e:0f:09:f3], cid=[no info], tid=0xd9e9c275: lease 169.254.200.3 will be advertised
INFO  EVAL_RESULT Expression sonic:dpu2 evaluated to 1
INFO  DHCP4_LEASE_ALLOC [hwtype=1 b0:cf:0e:0f:09:f3], cid=[no info], tid=0xd9e9c275: lease 169.254.200.3 has been allocated for 3600 seconds
INFO  EVAL_RESULT Expression sonic:dpu2 evaluated to 1
INFO  DHCP4_LEASE_ADVERT [hwtype=1 b0:cf:0e:0f:09:f3], cid=[01:b0:cf:0e:0f:09:f3], tid=0x18bb06e0: lease 169.254.200.3 will be advertised
INFO  EVAL_RESULT Expression sonic:dpu2 evaluated to 1
INFO  DHCP4_LEASE_ALLOC [hwtype=1 b0:cf:0e:0f:09:f3], cid=[01:b0:cf:0e:0f:09:f3], tid=0x18bb06e0: lease 169.254.200.3 has been allocated for 3600 seconds

Which release branch to backport (provide reason below if selected)

• 202205
• 202211
• 202305
• 202311
• 202405
• 202411
• 202505
• 202505

Tested branch (Please provide the tested image version)

Description for the changelog

Link to config_db schema for YANG module changes

A picture of a cute animal (not mandatory but encouraged)

[mssonicbld]

/azp run Azure.sonic-buildimage

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[gpunathilell]

@prabhataravind Please review

[mssonicbld]

/azp run Azure.sonic-buildimage

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