Migrate test_volume_boot_pattern to tempest client

Migrate the test and all shared or necessary functions from
OfficialClientTest to ScenarioTest. Create and update as well all
needed functions:

- server api schema
- servers_client

Partially implements: bp:tempest-client-scenarios

Change-Id: Ib9e70b6ce3814031d1b4b8987a24eb0992624204
Merge "Migrate test_volume_boot_pattern to tempest client"