BaseIdentityPlugin's username, password, and token_id properties
weren't properly deprecated since all they had was a comment in
the code. Proper deprecation requires use of warnings and
documentation.
Where the plugins already provide their own properties, the
properties need to be un-deprecated.
bp deprecations
Change-Id: Ic9fce89b8544d8c01f16e8f9c2f9dd2659d03c18
799e1faa50