TPac: Hide place hold links when not holdable

TPac: Hide place hold links when not holdable

The only check done is on the holdable flags:
Copy
Status
Location

Hold rules themselves are not checked.

Note that place hold links are shown either way when you can have the
PLACE_UNFILLABLE_HOLD permission and are logged into the staff client.

Signed-off-by: Thomas Berezansky <tsbere@mvlc.org>
Signed-off-by: Dan Scott <dscott@laurentian.ca>