userportal: fixed right-click context menu to match webadmin

Userportal's context menu style did not match the style used in webadmin.
It was missing a border, and the color and padding was wrong.
As far as I can tell, it has always been this way, and is probably an
oversight. Fixed.

Change-Id: I98d8ce62ba859863ce5b2b3cad5f65488d236ac2
Signed-off-by: Greg Sheremeta <gshereme@redhat.com>