Skip read-only test for CIFS

When using the CIFS protocol and trying to share a share by IP, the
share fails to instantiate and the manila service produces this error:

  InvalidShareAccessLevel: Invalid or unsupported share access level: ro.

There are no Manila Share backends that support CIFS shares with read
only access when authenticating with IP addresses[1]. This patch causes
the test to be skipped in such a case.

[1] https://docs.openstack.org/manila/latest/admin/share_back_ends_feature_support_mapping.html#mapping-of-share-drivers-and-share-access-rules-support

Change-Id: Ic30eaf3c2b7f75eb4bc62159faceb6bd30d7e03b
diff --git a/manila_tempest_tests/tests/scenario/test_share_basic_ops.py b/manila_tempest_tests/tests/scenario/test_share_basic_ops.py
index 1e23b82..6b54bdb 100644
--- a/manila_tempest_tests/tests/scenario/test_share_basic_ops.py
+++ b/manila_tempest_tests/tests/scenario/test_share_basic_ops.py
@@ -116,6 +116,11 @@
     @tc.attr(base.TAG_NEGATIVE, base.TAG_BACKEND)
     def test_write_with_ro_access(self):
         '''Test if an instance with ro access can write on the share.'''
+        if self.protocol.upper() == 'CIFS':
+            msg = ("Skipped for CIFS protocol because RO access is not "
+                   "supported for shares by IP.")
+            raise self.skipException(msg)
+
         test_data = "Some test data to write"
 
         instance = self.boot_instance(wait_until="BUILD")