Drop implementation to use pyOpenSSL to manage pkcs12 certs

The cryptography library has been bumped to 3.1 in upper-constraints
file during Ussuri, which is quite old. So we no longer have to
maintain logic for cryptography < 3.0.

Change-Id: I1a463e320b94b0e99e92541581e1ee5feffd356a
2 files changed