virsh-domain: Fix memleak in cmdUndefine with storage

When undefining a domain with storage when the volume isn't managed by
libvirt the name and path strings weren't freed properly.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=996050
(cherry picked from commit 5075248a)

tools/virsh-domain.c

@@ -3048,6 +3048,8 @@ cmdUndefine(vshControl *ctl, const vshCmd *cmd)
 
         for (i = 0; i < nvolumes; i++) {
             ctxt->node = vol_nodes[i];
+            VIR_FREE(source);
+            VIR_FREE(target);
 
             /* get volume source and target paths */
             if (!(target = virXPathString("string(./target/@dev)", ctxt)))
@@ -3090,6 +3092,8 @@ cmdUndefine(vshControl *ctl, const vshCmd *cmd)
             }
             vlist[nvols].source = source;
             vlist[nvols].target = target;
+            source = NULL;
+            target = NULL;
             nvols++;
         }
 
@@ -3189,6 +3193,8 @@ out:
     }
 
 cleanup:
+    VIR_FREE(source);
+    VIR_FREE(target);
     for (i = 0; i < nvols; i++) {
         VIR_FREE(vlist[i].source);
         VIR_FREE(vlist[i].target);