[fix] workaround postgres transaction clash

[muir]

CREATE SCHEMA IF NOT EXISTS can fail if another thread is creating the same schema at the same time.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 6 lines in your changes missing coverage. Please review.

Project coverage is 77.57%. Comparing base (d450e78) to head (5104ee4).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
lspostgres/postgres.go	50.00%	5 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #231      +/-   ##
==========================================
- Coverage   77.72%   77.57%   -0.15%     
==========================================
  Files          12       12              
  Lines        1257     1262       +5     
==========================================
+ Hits          977      979       +2     
- Misses        204      207       +3     
  Partials       76       76              

Flag	Coverage Δ
go_tests	9.09% <0.00%> (-0.05%)	⬇️
mysql_tests	50.81% <0.00%> (-0.28%)	⬇️
pg_tests	50.92% <50.00%> (-0.05%)	⬇️
singlestore_tests	46.27% <0.00%> (-0.26%)	⬇️

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