Server Upgrade: Allow base64 encoded values
This patch allows to use base64 encoded values in update files.
Double colon ('::') must be used as separator between attribute name
and base64 encoded value.
add:attr::<base64-value>
replace:attr::<old-base64-value>::<new-base64-value>
https://fedorahosted.org/freeipa/ticket/4984
Reviewed-By: Jan Cholasta <jcholast@redhat.com>