Add read-only tests for cephx access rules

In the Newton cycle the ability to create read-only rules for
cephx-backed access rules was added but there were no functional tests
to exercise this feature. This patchset adds new parameters to the
existing cephx access rule test to also test read-only rules.

Change-Id: I4b4fd5790526ebc596471fd913ffe9cdb2faa520
diff --git a/manila_tempest_tests/tests/api/test_rules.py b/manila_tempest_tests/tests/api/test_rules.py
index 024590d..1f227dd 100644
--- a/manila_tempest_tests/tests/api/test_rules.py
+++ b/manila_tempest_tests/tests/api/test_rules.py
@@ -422,13 +422,15 @@
     @tc.attr(base.TAG_POSITIVE, base.TAG_BACKEND)
     @ddt.data(*itertools.product(
         set(['2.13', '2.27', '2.28', LATEST_MICROVERSION]),
-        ("alice", "alice_bob", "alice bob")))
+        ("alice", "alice_bob", "alice bob"),
+        ('rw', 'ro')))
     @ddt.unpack
-    def test_create_delete_cephx_rule(self, version, access_to):
+    def test_create_delete_cephx_rule(self, version, access_to, access_level):
         rule = self.shares_v2_client.create_access_rule(
-            self.share["id"], self.access_type, access_to, version=version)
+            self.share["id"], self.access_type, access_to, version=version,
+            access_level=access_level)
 
-        self.assertEqual('rw', rule['access_level'])
+        self.assertEqual(access_level, rule['access_level'])
         for key in ('deleted', 'deleted_at', 'instance_mappings'):
             self.assertNotIn(key, rule.keys())
         self.shares_v2_client.wait_for_access_rule_status(