qa/tests: skip rgw site tests in api

Failure in https://jenkins.ceph.com/job/ceph-api/95185/

```
dashboard.rest_client.RequestException: RGW REST API GET timed out after 45 seconds (url=http://172.21.5.32:8000/admin/realm?list).
```

Signed-off-by: Nizamudeen A <[email protected]>

Author: nizamial09

qa/tasks/mgr/dashboard/helper.py

@@ -4,10 +4,12 @@
 
 import json
 import logging
+import os
 import random
 import re
 import string
 import time
+import unittest
 from collections import namedtuple
 from functools import wraps
 from typing import List, Optional, Tuple, Type, Union
@@ -756,3 +758,8 @@ def wrapper(*args, **kwargs):
             raise err
         return wrapper
     return decorator
+
+
+skip_unless_dashboard_pr = unittest.skipUnless(
+    os.environ.get('ghprbPullTitle', '').startswith('mgr/dashboard:'),
+    'Skipping because PR title does not start with mgr/dashboard')

qa/tasks/mgr/dashboard/test_rgw.py

@@ -10,7 +10,8 @@
 from cryptography.hazmat.primitives.hashes import SHA1
 from cryptography.hazmat.primitives.twofactor.totp import TOTP
 
-from .helper import DashboardTestCase, JLeaf, JList, JObj
+from .helper import (DashboardTestCase, JLeaf, JList, JObj,
+                     skip_unless_dashboard_pr)
 
 logger = logging.getLogger(__name__)
 
@@ -66,6 +67,7 @@ def get_rgw_user(self, uid, stats=True):
         return self._get('/api/rgw/user/{}?stats={}'.format(uid, stats))
 
 
+@skip_unless_dashboard_pr
 class RgwSiteTest(RgwTestCase):
 
     AUTH_ROLES = ['rgw-manager']