Code dedup in class TestServerActionRequestXMLDeserializer

Moved duplicated requests and expected replies to functions
-_generate_request()
-_generate_expected()

bp nova-tests-code-duplication

Change-Id: Ib1d1b8b93f769b8dd8223dbbb3c42288254d8825
Merge "Code dedup in class TestServerActionRequestXMLDeserializer"