Fixes #6808/BZ1124058: fixing permissions of product buttons.

Several product buttons were using the incorrect permission
in determining whether to disable the buttons.  This commit
fixes these incorrect permissions.

http://projects.theforeman.org/issues/6808
https://bugzilla.redhat.com/show_bug.cgi?id=1124058
I explicitly chose to keep it as `readonly` in case we change what readonly means in the future and to limit blast radius.