libxlDoMigrateReceive: Drop useless check for !vm

In the cleanup path, @vm cannot be possibly NULL. If it were so,
we would receive SIGSEGV much earlier. At the beginning of the
function we do libxlDomainObjBeginJob(.., vm, ..); and so on.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

src/libxl/libxl_migration.c

@@ -296,7 +296,7 @@ libxlDoMigrateReceive(void *opaque)
     libxlDomainObjEndJob(driver, vm);
 
  cleanup:
-    if (remove_dom && vm) {
+    if (remove_dom) {
         virDomainObjListRemove(driver->domains, vm);
         vm = NULL;
     }