pgsql: Release cache tuple when no longer needed

Release cache tuple when no longer needed

There was a small buglet in commit 52e4f0cd472d whereby a tuple acquired
from cache was not released, giving rise to WARNING messages; fix that.

While at it, restructure the code a bit on stylistic grounds.

Author: Hou zj <houzj(dot)fnst(at)fujitsu(dot)com>
Reported-by: Peter Smith <smithpb2250(at)gmail(dot)com>
Reviewed-by: Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAHut+PvKTyhTBtYCQsP6Ph7=o-oWRSX+v+PXXLXp81-o2bazig@mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ed0fbc8e5ac995eada933250c1d5535336442b97

Modified Files
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src/backend/commands/publicationcmds.c | 95 ++++++++++++++++---------------
src/test/regress/expected/publication.out | 16 ++++--
src/test/regress/sql/publication.sql | 8 +++
3 files changed, 68 insertions(+), 51 deletions(-)