Remove CredentialProvider deps to CONF

CredentialProvider uses CONF to get identity_version.
Identity version is always passed in anyways, so removing the CONF
dependency and making identity_version a mandatory parameter,
so that the class is ready for migration to tempest-lib

Partially implements: bp tempest-library
Change-Id: Ia960bf0b293e23537b3aaa8114bdbf7a46db62b1
8 files changed