Copy 'errno' and use copied value in the if check of retry in cluster migrate commands socket_err block.

[Shivshankar-Reddy]

errno is global variable and shared with system calls, so there is chance it may be overwritten during io free or close socket in migrate command code. It would be better it is copied before the free or closesocket and use copied value to check for retry in socket_err block. So added new variable to take copy and used the copy variable for the check. Thanks!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.59%. Comparing base (f89ff31) to head (9be7875).
Report is 2 commits behind head on unstable.

Additional details and impacted files

@@             Coverage Diff              @@
##           unstable    #1042      +/-   ##
============================================
+ Coverage     70.58%   70.59%   +0.01%     
============================================
  Files           114      114              
  Lines         61670    61672       +2     
============================================
+ Hits          43530    43540      +10     
+ Misses        18140    18132       -8     

Files with missing lines	Coverage Δ
src/cluster.c	88.13% <100.00%> (-0.26%)	⬇️

... and 8 files with indirect coverage changes