Bug 16591: Fix CSRF in opac-memberentry

Bug 16591: Fix CSRF in opac-memberentry

If an attacker can get an authenticated Koha user to visit their page
with the code below, they can update the victim's details to arbitrary
values.

Test plan:

Trigger
/cgi-bin/koha/opac-memberentry.pl?action=update&borrower_B_city=HACKED&borrower_firstname=KOHA&borrower_surname=test

=> Without this patch, the update will be done (or modification
request)
=> With this patch applied you will get a crash "Wrong CSRF token" (no
need to stylish)

Do some regression tests with this patch applied (Update patron infos)

QA note: I am not sure it's useful to create a digest of the DB pass,
but just in case...

Reported by Alex Middleton at Dionach.

Signed-off-by: Chris Cormack <chris@bigballofwax.co.nz>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>