PGPRO-646: Set need_repair before block_is_read

Author: za-arthur

src/backend/replication/walsender.c

@@ -2036,8 +2036,8 @@ ProcessStandbyRepairBlockMessage(void)
 	pg_write_barrier();
 
 	/* Send signal to backend that block is in shared memory */
-	RprBlockState->block_is_read = true;
 	RprBlockState->need_repair = false;
+	RprBlockState->block_is_read = true;
 	SetLatch(RprBlockState->backendLatch);
 
 	/* Set flag that walsenders are ready to repair another block */