Add missing volume RBAC test

Add missing RBAC test for 'show_group_type'
API [0] which enforces "group:access_group_type_specs"
according to policy in code docs [1].
[0]https://developer.openstack.org/api-ref/block-storage/v3/#show-group-type-details
[1]https://github.com/openstack/cinder/blob/76231f3ad2828fe7bb60ecd9686db807622bbb7a/cinder/policies/group_types.py#L53

Change-Id: I71c81d0798082c03408d75deb021e7fcf077b938
diff --git a/patrole_tempest_plugin/tests/api/volume/test_groups_rbac.py b/patrole_tempest_plugin/tests/api/volume/test_groups_rbac.py
index 20f20a5..192e1c4 100644
--- a/patrole_tempest_plugin/tests/api/volume/test_groups_rbac.py
+++ b/patrole_tempest_plugin/tests/api/volume/test_groups_rbac.py
@@ -148,7 +148,21 @@
         service="cinder",
         rule="group:group_types_manage")
     def test_delete_group_type(self):
-        goup_type = self.create_group_type(ignore_notfound=True)
+        group_type = self.create_group_type(ignore_notfound=True)
 
         self.rbac_utils.switch_role(self, toggle_rbac_role=True)
-        self.group_types_client.delete_group_type(goup_type['id'])
+        self.group_types_client.delete_group_type(group_type['id'])
+
+    @decorators.idempotent_id('8d9e2831-24c3-47b7-a76a-2e563287f12f')
+    @rbac_rule_validation.action(
+        service="cinder",
+        rule="group:access_group_types_specs")
+    def test_show_group_type(self):
+        group_type = self.create_group_type()
+        self.rbac_utils.switch_role(self, toggle_rbac_role=True)
+        resp_body = \
+            self.group_types_client.show_group_type(
+                group_type['id'])['group_type']
+        if 'group_specs' not in resp_body:
+            raise rbac_exceptions.RbacMalformedResponse(
+                attribute='group_specs')