gitlab_runner: Make owned and project mutually exclusive (#4136) (#4210)

* gitlab_runner: Set owned and project mutually exclusive

* gitlab_runner : Refactor _runners_endpoint usage

(cherry picked from commit 05c3e0d69f)

Co-authored-by: Léo GATELLIER <26511053+lgatellier@users.noreply.github.com>

tests/unit/plugins/modules/source_control/gitlab/gitlab.py

@@ -17,8 +17,9 @@ import gitlab
 
 
 class FakeAnsibleModule(object):
-    def __init__(self):
+    def __init__(self, module_params=None):
         self.check_mode = False
+        self.params = module_params if module_params else {}
 
     def fail_json(self, **args):
         pass