Add alt project persona in dynamic credential

Tempest dynamic credential does not support two
separate project admin or reader but sometime we need to
check the test behavior by requesting API with
different project admin or reader role.

This commit add support of alt project admin and reader,
also provide consistent method name for alt project member
role.

Change-Id: I11248fd0906d910180be30de7b59231e534b4563
6 files changed