Reject requests after getting close session request.

[dcherednik]

Attempt to fix race reproduced by CloseSessionsWithLoad test:

• Kqp request can came just after close session request. In this case there is a gap when session actor is already DEAD but kqp proxy stil has a record in the local sessions.

Changelog category

• Bugfix

[github-actions]

⚪ 2024-12-13 15:40:48 UTC Pre-commit check linux-x86_64-relwithdebinfo for 167337e has started.
⚪ 2024-12-13 15:41:00 UTC Artifacts will be uploaded here
⚪ 2024-12-13 15:44:02 UTC ya make is running...
🟡 2024-12-13 16:37:21 UTC Some tests failed, follow the links below. Going to retry failed tests...

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
20735	19208	0	4	1410	113

⚪ 2024-12-13 16:39:02 UTC ya make is running... (failed tests rerun, try 2)
🟢 2024-12-13 16:51:03 UTC Tests successful.

Test history | Ya make output | Test bloat | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
683 (only retried tests)	576	0	0	0	107

🟢 2024-12-13 16:51:12 UTC Build successful.
🟢 2024-12-13 16:51:34 UTC ydbd size 2.1 GiB changed* by +944 Bytes, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 31afdb8	merge: 167337e	diff	diff %
ydbd size	2 258 161 872 Bytes	2 258 162 816 Bytes	+944 Bytes	+0.000%
ydbd stripped size	484 299 920 Bytes	484 300 048 Bytes	+128 Bytes	+0.000%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}

[github-actions]

⚪ 2024-12-13 15:41:03 UTC Pre-commit check linux-x86_64-release-asan for 167337e has started.
⚪ 2024-12-13 15:41:15 UTC Artifacts will be uploaded here
⚪ 2024-12-13 15:44:19 UTC ya make is running...
🟡 2024-12-13 16:49:08 UTC Some tests failed, follow the links below. This fail is not in blocking policy yet

Test history | Ya make output | Test bloat

TESTS	PASSED	ERRORS	FAILED	SKIPPED	MUTED?
13218	13144	0	19	9	46

🟢 2024-12-13 16:50:20 UTC Build successful.
🟢 2024-12-13 16:50:44 UTC ydbd size 3.6 GiB changed* by +3.1 KiB, which is < 100.0 KiB vs main: OK

ydbd size dash	main: 31afdb8	merge: 167337e	diff	diff %
ydbd size	3 902 464 424 Bytes	3 902 467 624 Bytes	+3.1 KiB	+0.000%
ydbd stripped size	1 367 972 592 Bytes	1 367 973 360 Bytes	+768 Bytes	+0.000%

^{*please be aware that the difference is based on comparing your commit and the last completed build from the post-commit, check comparation}