Correctly initialise shared recoveryLastRecPtr in recovery.

Previously we used ReadRecPtr rather than EndRecPtr, which was
not a serious error but caused pg_stat_replication to report
incorrect replay_location until at least one WAL record is replayed.

Fujii Masao

Author: simonat2ndQuadrant

src/backend/access/transam/xlog.c

@@ -6451,7 +6451,7 @@ StartupXLOG(void)
 		 */
 		SpinLockAcquire(&xlogctl->info_lck);
 		xlogctl->replayEndRecPtr = ReadRecPtr;
-		xlogctl->recoveryLastRecPtr = ReadRecPtr;
+		xlogctl->recoveryLastRecPtr = EndRecPtr;
 		xlogctl->recoveryLastXTime = 0;
 		xlogctl->recoveryPause = false;
 		SpinLockRelease(&xlogctl->info_lck);