Fix crash if LockErrorCleanup() is called twice

The refactoring in commit 3c0fd64fec removed the clearing of
awaitedLock from LockErrorCleanup(). It's still needed, otherwise
LockErrorCleanup() during abort processing will try to update the
LOCALLOCK struct even after the lock has already been released. Put it
back.

Reported-by: Richard Guo <guofenglinux@gmail.com>
Reported-by: Robins Tharakan <tharakan@gmail.com>
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Discussion: https://www.postgresql.org/message-id/flat/CAMbWs4_dNX1SzBmvFdoY-LxJh_4W_BjtVd5i008ihfU-wFF=eg@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/18832-38e5575b1bbd7277@postgresql.org
Discussion: https://www.postgresql.org/message-id/e11a30e5-c0d8-491d-8546-3a1b50c10ad4@gmail.com

src/backend/storage/lmgr/lock.c

@@ -1896,6 +1896,15 @@ GetAwaitedLock(void)
 	return awaitedLock;
 }
 
+/*
+ * ResetAwaitedLock -- Forget that we are waiting on a lock.
+ */
+void
+ResetAwaitedLock(void)
+{
+	awaitedLock = NULL;
+}
+
 /*
  * MarkLockClear -- mark an acquired lock as "clear"
  *

src/backend/storage/lmgr/proc.c

@@ -814,6 +814,8 @@ LockErrorCleanup(void)
 			GrantAwaitedLock();
 	}
 
+	ResetAwaitedLock();
+
 	LWLockRelease(partitionLock);
 
 	RESUME_INTERRUPTS();