wait_until_merge_status_is_set: always query merge request

The function used to rely on the given merge request object without
checking its current state. If the given object was not in one of the
"unchecked" states, it returned immediately. The state, however, could
have changed between its last query and the call of this function, so
it now checks the state first before deciding anything.

common.py

@@ -99,6 +99,7 @@ def wait_until_merge_status_is_set(project: Project, mr: MergeRequest):
     """Periodically query MR until GitLab has checked its merge status"""
     print("Waiting until merge status has been checked", end="", flush=True)
     unchecked_states = ["unchecked", "checking", "cannot_be_merged_recheck"]
+    mr = project.mergerequests.get(mr.iid, retry_transient_errors=True)
     while mr.merge_status in unchecked_states:
         print(".", end="", flush=True)
         time.sleep(1)