Fix bug introduced by the recent patch to check that the checkpoint redo

location read from backup label file can be found: wasShutdown was set
incorrectly when a backup label file was found.

Jeff Davis, with a little tweaking by me.

src/backend/access/transam/xlog.c

@@ -5864,6 +5864,7 @@ StartupXLOG(void)
 		if (record != NULL)
 		{
 			memcpy(&checkPoint, XLogRecGetData(record), sizeof(CheckPoint));
+			wasShutdown = (record->xl_info == XLOG_CHECKPOINT_SHUTDOWN);
 			ereport(DEBUG1,
 					(errmsg("checkpoint record is at %X/%X",
 							checkPointLoc.xlogid, checkPointLoc.xrecoff)));
@@ -5888,6 +5889,7 @@ StartupXLOG(void)
 			ereport(FATAL,
 					(errmsg("could not locate required checkpoint record"),
 					 errhint("If you are not restoring from a backup, try removing the file \"%s/backup_label\".", DataDir)));
+			wasShutdown = false; /* keep compiler quiet */
 		}
 		/* set flag to delete it later */
 		haveBackupLabel = true;
@@ -5932,10 +5934,10 @@ StartupXLOG(void)
 					 (errmsg("could not locate a valid checkpoint record")));
 		}
 		memcpy(&checkPoint, XLogRecGetData(record), sizeof(CheckPoint));
+		wasShutdown = (record->xl_info == XLOG_CHECKPOINT_SHUTDOWN);
 	}
 
 	LastRec = RecPtr = checkPointLoc;
-	wasShutdown = (record->xl_info == XLOG_CHECKPOINT_SHUTDOWN);
 
 	ereport(DEBUG1,
 			(errmsg("redo record is at %X/%X; shutdown %s",