After upgrading a deployment from CA-less to CA-ful it is necessary
to install the RA Agent credential on non-CA servers. To facilitate
this, extract this behaviour from CAInstance so that it is callable
from other code.
Several other methods became @staticmethod as a result of this
change. This makes those methods callable without an instance of
CAInstance and also documents that those methods do not use 'self'.
Part of: https://pagure.io/freeipa/issue/7188
Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
a1b3b34b90