Fix use-after-free bug when renaming constraints

Michael Paquier <michael@paquier.xyz>

Commit: 91fc2a08830139d9c11b189a2407cfdf113f550f
Author: Michael Paquier <michael@paquier.xyz>
Date: 2018-12-17T03:43:48Z
Releases: 10.7
Fix use-after-free bug when renaming constraints

This is an oversight from recent commit b13fd344.  While on it, tweak
the previous test with a better name for the renamed primary key.

Detected by buildfarm member prion which forces relation cache release
with -DRELCACHE_FORCE_RELEASE.  Back-patch down to 9.4 as the previous
commit.

Files