Make standby promotion reset the recovery pause state to 'not paused'.

If a promotion is triggered while recovery is paused, the paused state ends
and promotion continues. But previously in that case
pg_get_wal_replay_pause_state() returned 'paused' wrongly while a promotion
was ongoing.

This commit changes a standby promotion so that it marks the recovery
pause state as 'not paused' when it's triggered, to fix the issue.

Author: Fujii Masao
Reviewed-by: Dilip Kumar, Kyotaro Horiguchi
Discussion: https://postgr.es/m/f706876c-4894-0ba5-6f4d-79803eeea21b@oss.nttdata.com

src/backend/access/transam/xlog.c

@@ -12825,6 +12825,14 @@ SetPromoteIsTriggered(void)
 	XLogCtl->SharedPromoteIsTriggered = true;
 	SpinLockRelease(&XLogCtl->info_lck);
 
+	/*
+	 * Mark the recovery pause state as 'not paused' because the paused state
+	 * ends and promotion continues if a promotion is triggered while recovery
+	 * is paused. Otherwise pg_get_wal_replay_pause_state() can mistakenly
+	 * return 'paused' while a promotion is ongoing.
+	 */
+	SetRecoveryPause(false);
+
 	LocalPromoteIsTriggered = true;
 }