Drop test user when done with it.

Tom Lane <tgl@sss.pgh.pa.us>

Commit: f31111bbe81db0e84fb486c6423a234c47091b30
Author: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2019-06-24T16:36:51Z
Releases: 12.0
Drop test user when done with it.

Commit d7f8d26d9 added a test case that created a user, but forgot
to drop it again.  This is no good; for one thing, it causes repeated
"make installcheck" runs to fail.

Files