Add unit test to check non-string password support

Non-string passwords from keystoneclient are converted but
we are not testing it so adding in a test case for this.

Co-authored-by: r-sekine <r-sekine@intellilink.co.jp>
Fixes: bug #1210099

Change-Id: I666e9e0b7ce10d6efed9d98aee0dac09cf2cd066