Fix unstable assertion in test_cinder_endpoints

In simple_read_only.test_cinder.test_cinder_endpoints, the test case
assumes that the first table of 'cinder endpoints' always ['nova',
'Value']. However, it is sometimes wrong.
So in this commit, the test verifies that they have 2 or more headers
and has a 'Value' header.

Change-Id: Idb3f2ebc6b7e05178621ac3701b7c3d02e1d7591
Closes-Bug: #1363018
Closes-Bug: #1362703
Migrate test_server_cfn_init to tempest clients

Migrate the test and change OrchestrationScenarioTest used by the test.
This is a part of the migrating all scenario tests to using tempest own
clients.

Change-Id: Iafc1b021fe8a9a5daa0e2d7eef0542b7929c415a
Partially-implements: bp:tempest-client-scenarios
Typo fixes "tryies", "snaphot", "Retruns"

Misspellings and grammatical errors found in docstrings
of test.py

Change-Id: Id4d548fa4ae00056aca7434b878eaf8eb09333cc
Merge "Migrate test_server_cfn_init to tempest clients"
Merge "Typo fixes "tryies", "snaphot", "Retruns""
Merge "Fix unstable assertion in test_cinder_endpoints"
Merge branch 'master' of https://github.com/openstack/tempest