Don't run playbooks if role count == 0

There is no reason to try to run playbooks limited
to a role name when the role count is zero. It
actually fails because no hosts match.

Add a check to skip roles with count == 0.

Closes-Bug: #1955432
Change-Id: I5312e5362bdeac8337d1d0991e5a94ded5e83f3f

tripleoclient/tests/test_utils.py

@@ -406,6 +406,8 @@ class TestRunRolePlaybooks(TestCase):
     @mock.patch('tripleoclient.utils.run_ansible_playbook')
     def test_role_playbooks(self, mock_run):
         roles = [
+            # No playbooks should execute for the role if count is 0.
+            {'count': 0, 'name': 'ZeroNodesRole'},
             {'count': 10, 'name': 'Compute'},
             {
                 'count': 3,

tripleoclient/utils.py

@@ -3002,6 +3002,9 @@ def run_role_playbooks(self, working_dir, roles_file_dir, roles,
 
     # Pre-Network Config
     for role in roles:
+        if role.get('count', 1) == 0:
+            continue
+
         role_playbooks = []
 
         for x in role.get('ansible_playbooks', []):