Added default injected files to test_create_server and test_rebuild_server

* Added call to get_default_injected_files to test_create_server and
  test_rebuild_server. This will allow these tests to inject any neccesary
  files into their server build process.
* Added logic to prevent passed in or test level personality files being
  overwritten by default injected files
* Added logic in test_rebuild_servers to allow for a 'None' value in
  the default_injected_files

Change-Id: I6ac7538073610b17fc5912342f89a0dd41d27165
Merge "Added default injected files to test_create_server and test_rebuild_server"