Handle quarantine/delete functions for some hazardous paths

Migrated from: https://tracker.clearos.com/view.php?id=3411

Reported by: Peter Baldwin

The quarantine/delete function should be hidden for files in certain parts of the file system, notably:

/var/spool/imap
/var/spool/squid

Alternatively, add the delete/quarantine function needs to delete these files in a different way (cyradm? /usr/bin/purge from Squid?).

Note: Squid might work just fine with such an action, but Cyrus IMAP is definitely not happy.

Developer comment:

cyrus-imap recovers overnight.