LP#1789747: tweak disabling the offline circulation link

LP#1789747: tweak disabling the offline circulation link

This patch ensures that the menu link can be fully disabled by
giving the "disabled" CSS class to the anchor as well as the
li that contains it. It also adds a CSS rule to the disabled
class to force the cursor to not-allowed; due to a quirk, an
anchor with "pointer-events: none" will not respect "cursor: not-allowed",
but the containing element can have that cursor rule.

Signed-off-by: Galen Charlton <gmc@equinoxinitiative.org>