Remove reindex_catalog test from test schedules.

As none of the approaches for avoiding the deadlock issues seem
promising enough, and all the expected reindex related changes have
been made, apply 60c2951e1bab7e to master as well.

Discussion: https://postgr.es/m/4622.1556982247@sss.pgh.pa.us

src/test/regress/expected/reindex_catalog.out

 --
 -- Check that system tables can be reindexed.
 --
--- Note that this test currently has to run without parallel tests
--- being scheduled, as currently reindex catalog tables can cause
+-- Note that this test currently is not included in the default
+-- schedules, as currently reindexing catalog tables can cause
 -- deadlocks:
 --
 -- * The lock upgrade between the ShareLock acquired for the reindex
@@ -16,6 +16,11 @@
 --   tables are routinely released before commit - therefore the lock
 --   held for reindexing doesn't guarantee that no running transaction
 --   performed modifications in the table underlying the index.
+--
+--   This is particularly problematic as such conflicts can be
+--   triggered even when run in isolation, as a previous session's
+--   temporary table cleanup might still be running (even when the
+--   session ended from a client perspective).
 -- Check reindexing of whole tables
 REINDEX TABLE pg_class; -- mapped, non-shared, critical
 REINDEX TABLE pg_index; -- non-mapped, non-shared, critical

src/test/regress/parallel_schedule

@@ -52,11 +52,6 @@ test: create_misc create_operator create_procedure
 # These depend on create_misc and create_operator
 test: create_index create_index_spgist create_view index_including index_including_gist
 
-# ----------
-# Has to run in isolation, due to deadlock risk
-# ----------
-test: reindex_catalog
-
 # ----------
 # Another group of parallel tests
 # ----------

src/test/regress/serial_schedule

@@ -66,7 +66,6 @@ test: create_index_spgist
 test: create_view
 test: index_including
 test: index_including_gist
-test: reindex_catalog
 test: create_aggregate
 test: create_function_3
 test: create_cast

src/test/regress/sql/reindex_catalog.sql

 --
 -- Check that system tables can be reindexed.
 --
--- Note that this test currently has to run without parallel tests
--- being scheduled, as currently reindex catalog tables can cause
+-- Note that this test currently is not included in the default
+-- schedules, as currently reindexing catalog tables can cause
 -- deadlocks:
 --
 -- * The lock upgrade between the ShareLock acquired for the reindex
@@ -16,6 +16,11 @@
 --   tables are routinely released before commit - therefore the lock
 --   held for reindexing doesn't guarantee that no running transaction
 --   performed modifications in the table underlying the index.
+--
+--   This is particularly problematic as such conflicts can be
+--   triggered even when run in isolation, as a previous session's
+--   temporary table cleanup might still be running (even when the
+--   session ended from a client perspective).
 
 
 -- Check reindexing of whole tables