The mTLS OAuth2.0 in Keystone uses a parameter that is only availble on
cryptography 36.0.0 or later. Users may have to upgrade cryptography
which is already installed, which can be unreasonably hassle. This
patch introduces an alternative for that parameter.
[1] https://cryptography.io/en/latest/changelog/#v36-0-0
Closes-bug: 2009600
Change-Id: Idffe269b62797bb2935429f4069e878a177db04f