virsh: Use inactive definition when removing disk from config

https://bugzilla.redhat.com/show_bug.cgi?id=1049529

The 'detach-disk' command in virsh used the active XML definition of a
domain even when attempting to remove a disk from the config only. If
the disk was only in the inactive definition the operation failed. Fix
this by using the inactive XML in case that only the config is affected.

tools/virsh-domain.c

@@ -10175,7 +10175,12 @@ cmdDetachDisk(vshControl *ctl, const vshCmd *cmd)
     if (vshCommandOptStringReq(ctl, cmd, "target", &target) < 0)
         goto cleanup;
 
-    if (!(doc = virDomainGetXMLDesc(dom, 0)))
+    if (flags == VIR_DOMAIN_AFFECT_CONFIG)
+        doc = virDomainGetXMLDesc(dom, VIR_DOMAIN_XML_INACTIVE);
+    else
+        doc = virDomainGetXMLDesc(dom, 0);
+
+    if (!doc)
         goto cleanup;
 
     if (persistent &&