pgsql: Fix another Assert issue exposed by CLOBBER_CACHE_ALWAYS.

Fix another Assert issue exposed by CLOBBER_CACHE_ALWAYS.

plpgsql's exec_stmt_execsql was Assert'ing that a CachedPlanSource was
is_valid immediately after exec_prepare_plan.  The risk factor in this case
is that after building the prepared statement, exec_prepare_plan calls
exec_simple_check_plan, which might try to generate a generic plan --- and
with CLOBBER_CACHE_ALWAYS or other unusual causes of invalidation, that
could result in an invalidation.  However, that path could only be taken
for a SELECT query, for which we need not set mod_stmt.  So in this case
I think it's best to just remove the Assert; it's okay to look at a
slightly-stale querytree for what we need here.  Per buildfarm testing.

Branch
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master

Details
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http://git.postgresql.org/pg/commitdiff/faf5cee7f0189beba206a5d96c0abd8e4382b844

Modified Files
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src/pl/plpgsql/src/pl_exec.c |    1 -
1 files changed, 0 insertions(+), 1 deletions(-)