Change manila_tempest_tests to use credentials_factory

With the merge of 'Factor up config dependent credential classes' in tempest,
(Change-Id: I351f86f0570070105bbf24f2d904e917feea6e57)
helper methods related to credentials have been moved to
common.credentials_factory module.
manila_tempest_tests need to change accordingly.

Change-Id: I9e5c72279638e07f509a4bfe0174b5ad5ee70b45
Closes-Bug: #1519612
3 files changed
tree: 7c77912e08de89b890727eaf5a5e774f76e89ef6
  1. manila_tempest_tests/