lxc: Use virDomainObjEndAPI after FindByName

For consistency, rather than open coding the Unref and Unlock,
just use the virDomainObjEndAPI API.
Signed-off-by: NJohn Ferlan <jferlan@redhat.com>

src/lxc/lxc_process.c

@@ -420,8 +420,7 @@ static int virLXCProcessSetupNamespaceName(virConnectPtr conn, int ns_type, cons
 
  cleanup:
     VIR_FREE(path);
-    virObjectUnlock(vm);
-    virObjectUnref(vm);
+    virDomainObjEndAPI(&vm);
     return fd;
 }