Merge r5160: Flush log on backend close

Add explicit log flushing when backend connections close to keep log
chronology. This is to avoid log lines for the same (reused) FD coming
before the closing connection when load is high.

Fixes #739



git-svn-id: http://www.varnish-cache.org/svn/branches/2.1@5341 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_backend.c

@@ -345,6 +345,11 @@ vbe_GetVbe(struct sess *sp, struct backend *bp)
 		}
 		VSL_stats->backend_toolate++;
 		WSL(sp->wrk, SLT_BackendClose, vc->fd, "%s", bp->vcl_name);
+
+		/* Checkpoint log to flush all info related to this connection
+		   before the OS reuses the FD */
+		WSL_Flush(sp->wrk, 0);
+
 		TCP_close(&vc->fd);
 		VBE_DropRefConn(bp);
 		vc->backend = NULL;