Refactor the openvswitch directory

[hwchiu]

• Create a new object OVSManager and it contains the ovs.Client object.
• All the OVS function is a member function of OVSManager, hence we only init the ovs.Client once for a series OVS operation
• The server side object server contains the OVSManager

[codecov]

Codecov Report

Merging #14 into master will increase coverage by 4.46%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #14      +/-   ##
==========================================
+ Coverage   75.21%   79.67%   +4.46%     
==========================================
  Files           4        5       +1     
  Lines         117      123       +6     
==========================================
+ Hits           88       98      +10     
+ Misses         20       18       -2     
+ Partials        9        7       -2

Impacted Files	Coverage Δ
openvswitch/ovs.go	100% <100%> (+7.69%)	⬆️
utils/utils.go	100% <0%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 0db9fd3...10143fa. Read the comment docs.