ipaclient role: Fix naming of modules, action_plugins and registered vars

The naming in the ipaclient role has not been following the naming scheme
and conventions used in the ipaserver and ipareplica roles. Also registered
results of modules and commands have not been unsing the result_ prefix as
in the other roles. All this has been fixed and the naming is consistent
now.

These are the renames:

ipahost -> ipaclient_get_otp
ipaapi -> ipaclient_api
ipaextras -> ipaclient_extras
ipafixca -> ipaclient_fix_ca
ipafstore -> ipaclient_fstore
ipa_facts -> ipaclient_get_facts
ipahost -> ipaclient_get_otp
ipajoin -> ipaclient_join
ipanss -> ipaclient_setup_nss
ipasssd -> ipaclient_setup_sssd
ipadiscovery -> ipaclient_test
ipatest -> ipaclient_test_keytab