Adding four new test cases to "import zone" test suite

1) "test_create_zone_import_invalid_ttl"
   Use invalid TTL value to create zone import.
   Expected: should fail.

2) "test_create_zone_import_invalid_name"
   Use invalid name to create zone import.
   Expected: should fail

3) "test_show_import_impersonate_another_project"
   Use admin client to impersonate another project and to
   show created zone imports.
   Note: test is based on "x-auth-sudo-project-id" HTTP header.

4) "test_list_import_zones_all_projects"
   Use admin client to list all created zone imports.
   Note: test is based on "x-auth-all-projects" HTTP header.

Change-Id: Icca248d21ccb495d438ff828a79c0894690792f1
diff --git a/designate_tempest_plugin/common/constants.py b/designate_tempest_plugin/common/constants.py
index 7ebcc87..2d3f70e 100644
--- a/designate_tempest_plugin/common/constants.py
+++ b/designate_tempest_plugin/common/constants.py
@@ -12,5 +12,10 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-# API statuses
+# Designate statuses strings
+PENDING = 'PENDING'
+COMPLETE = 'COMPLETE'
+ERROR = 'ERROR'
+DELETED = 'DELETED'
+ACTIVE = 'ACTIVE'
 UP = 'UP'