9660srv leaked memory on each walk if the destination
can't be found.

Reference: /n/sources/patch/applied/9660srv-walk-leak
Date: Fri Jun 17 10:52:06 CES 2011
Signed-off-by: cinap_lenrek@gmx.de

--- /sys/src/cmd/9660srv/main.c	Fri Jun 17 10:50:03 2011
+++ /sys/src/cmd/9660srv/main.c	Fri Jun 17 10:50:01 2011
@@ -246,6 +246,7 @@
 	p = malloc(n);
 	if(p == 0)
 		error("no memory");
+	setmalloctag(p, getcallerpc(&n));
 	return p;
 }
 
@@ -365,8 +366,6 @@
 	}
 
 	if(waserror()){
-		if(nf != nil)
-			xfile(req->newfid, Clunk);
 		if(rep->nwqid == req->nwname){
 			if(oldlen)
 				free(oldptr);
@@ -378,6 +377,8 @@
 			f->ptr = oldptr;
 			f->len = oldlen;
 		}
+		if(nf != nil)
+			xfile(req->newfid, Clunk);
 		if(rep->nwqid==req->nwname || rep->nwqid > 0){
 			err_msg[0] = '\0';
 			return;