luci: Don't remove attributes from xvm fence devs in non-expert mode
If attributes are set on an xvm fence device that are only shown in
expert mode, and the device is edited in non-expert mode, the
attributes that are shown only in expert mode are removed. This patch
corrects that.
Resolves: rhbz#1004011
Signed-off-by: Ryan McCabe <rmccabe@redhat.com>