oo-admin-ctl-domain: Allow addition of ssh key to domain through 'update' action

Bug 1088405
Bugzilla link https://bugzilla.redhat.com/show_bug.cgi?id=1088405
The update action will now check to see if a ssh key has been provided before providing the error that not enough parameters were provided. This allows us to use the already-written ssh key addition code.