Properly return PostgreSQL errors on geo-replication-resume

What does this MR do?

Before this PR, the exception included the stdout of the query execution. This wasn't helpful because on errors, psql logs to stderr:

root@foo.gitlab01:~# gitlab-psql 'SELECT foo;' > /dev/null
psql: error: could not connect to server: No such file or directory
	Is the server running locally and accepting
	connections on Unix domain socket "/var/opt/gitlab/postgresql/.s.PGSQL.5432"?
root@foo.gitlab01:~# gitlab-psql 'SELECT foo;' 2> /dev/null

This led to the unhelpful error message:

root@foo.gitlab01:~# gitlab-ctl geo-replication-resume
* Resume replication
Postgres encountered an error: Unable to resume postgres replication

With the new stderr logging, this will look like this:

root@foo.gitlab01:~# gitlab-ctl geo-replication-resume
* Resume replication
Postgres encountered an error:
 Unable to resume postgres replication psql: error: could not connect to server: No such file or directory
	Is the server running locally and accepting
	connections on Unix domain socket "/var/opt/gitlab/postgresql/.s.PGSQL.5432"?

Related issues

Checklist

See Definition of done.

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Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
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Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
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