[IMP] runbot_merge: acknowledge check command

The command works, but the 'bot would always reply it was not allowed

runbot_merge/models/pull_requests.py

@@ -805,6 +805,7 @@ class PullRequests(models.Model):
                         'repository': self.repository.id,
                         'number': self.number,
                     })
+                    ok = True
             elif command == 'review':
                 if self.draft:
                     msg = "Draft PRs can not be approved."