libxl: Add refcnt for args->conn during migration

Since the @dconn reference via args->conn will be used via a thread
or callback, let's make sure memory associated with it isn't free'd
unexpectedly before we use it. The Unref will be done when the object
is Dispose'd.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>
Reviewed-by: NMarc Hartmayer <mhartmay@linux.vnet.ibm.com>
Reviewed-by: NErik Skultety <eskultet@redhat.com>

src/libxl/libxl_migration.c

@@ -239,6 +239,7 @@ libxlMigrationDstArgsDispose(void *obj)
 
     libxlMigrationCookieFree(args->migcookie);
     VIR_FREE(args->socks);
+    virObjectUnref(args->conn);
     virObjectUnref(args->vm);
 }
 
@@ -608,7 +609,7 @@ libxlDomainMigrationDstPrepareTunnel3(virConnectPtr dconn,
     if (!(args = virObjectNew(libxlMigrationDstArgsClass)))
         goto error;
 
-    args->conn = dconn;
+    args->conn = virObjectRef(dconn);
     args->vm = virObjectRef(vm);
     args->flags = flags;
     args->migcookie = mig;
@@ -763,7 +764,7 @@ libxlDomainMigrationDstPrepare(virConnectPtr dconn,
     if (!(args = virObjectNew(libxlMigrationDstArgsClass)))
         goto error;
 
-    args->conn = dconn;
+    args->conn = virObjectRef(dconn);
     args->vm = virObjectRef(vm);
     args->flags = flags;
     args->socks = socks;