[SDK] Fix deadlock when shuting down http client

[owent]

Fixes #2336

Changes

• Reduce critical section of session_ids_m_ in http client.

For significant contributions please make sure you have completed the following items:

• CHANGELOG.md updated for non-trivial changes
• Unit tests have been added
• Changes in public API reviewed

[codecov]

Codecov Report

Merging #2337 (ca8908a) into main (a45081a) will increase coverage by 0.02%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main    #2337      +/-   ##
==========================================
+ Coverage   87.43%   87.45%   +0.02%     
==========================================
  Files         199      199              
  Lines        5997     5997              
==========================================
+ Hits         5243     5244       +1     
+ Misses        754      753       -1     

see 1 file with indirect coverage changes

[marcalff]

The change itself looks good, and reduces the amount of code executed under a lock, so approved.

Unsure if:

• we know for sure that the root cause of the deadlock found was related to the critical sections involved in this patch, so the root cause is fixed
• we do not know the exact root cause of the deadlock found, so this fix will improve things in general but a deadlock may still exist.

Please clarify.