Adds new scenario test to the Zones suite + minor refactoring

Test name: "test_create_and_update_zone"
   1. Create a Zone using particular TTL and Description values.
   2. Update Zone's TTL and Description.
   3. Make sure that the updated values presents in "Show Zone".

Change-Id: Ic9aa12eb9fd9cdad8f6f765cc98de20b272aaf33
2 files changed