Mark old email address as 'On hold' after edit or delete

When an active email address is edited or deleted, re-add the old
value as an 'on hold' address, so that it will be exported in the
suppression list and we don't keep sending mail to people's old
addresses.  Should allow you to delete 'on hold' addresses without
re-adding them.

Change-Id: Ia5b4d4383812655c0a98b8cd3089b150a9a2be9d
Merge "Mark old email address as 'On hold' after edit or delete"