Fix connection search path being reset

What does this MR do?

RESET ALL is reseting too many parameters, we should reset only the parameter we just set, namely statement_timeout

https://www.postgresql.org/docs/12/sql-reset.html

In #337813 (closed), we are planning to use PostgreSQL database schemas to separate tables. To do so in a backwards compatible way we need to set the search_path configuration parameter. Unfortunately, tests fail (example: https://gitlab.com/gitlab-org/gitlab/-/jobs/1484972168) because anytime we hit this method, all configuration parameters are reset to their default values, all tests after that fails.

We should not be resetting all parameters anyway - we only need to reset the one that we just manipulated, namely statement_timeout.

Related issue: #337813 (closed)

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