With the support for Random Serial Numbers v3 in FreeIPA 4.10, the
attribute random_serial_numbers has been added to the installer options.

options._random_serial_numbers is generated by ca.install_check and
later used by ca.install in the _setup_ca module.

ca.install_check is using options.random_serial_numbers and generating
options._random_serial_numbers which is later used by ca.install in
ca.install the _setup_ca module.

Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2103928
       https://bugzilla.redhat.com/show_bug.cgi?id=2103924