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.

Trunk r5160 reworked for 2.1 branch.



git-svn-id: http://www.varnish-cache.org/svn/branches/2.1@5161 d4fa192b-c00b-0410-8231-f00ffab90ce4

bin/varnishd/cache_backend.c

@@ -386,6 +386,11 @@ VBE_ClosedFd(struct sess *sp)
 	bp = sp->vbe->backend;
 
 	WSL(sp->wrk, SLT_BackendClose, sp->vbe->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(&sp->vbe->fd);
 	VBE_DropRefConn(bp);
 	sp->vbe->backend = NULL;