Add test for showing encryption specs item

This patch adds test for the missing API (volume v2):
show specific encryption specs item for a volume type.

Including:

[1] Add show encryption specs item API to v2 encryption_types_client
[2] Add unit test for the API
[3] Modify test case: test_volume_type_encryption_create_get_update_delete
[4] Add release note

Change-Id: Idd91e39716f4acf6796412f3f67ef8b6771916f9
4 files changed