Bug 1380200 - make sure main two do not have 'none' option
Bug 1380829 - make sure the previous default email method is respected

On upgrade from 1.9 the default core notifications 'System message'
and 'Message from other users' can be set to 'none' - which is not
allowed.

This patch will fix that problem by making sure the default core
notifications are set to email and that any users are also updated to
beusing the newly set default method.

Also deals with setting the default email method correctly - the prev
change to notifications didn't set the default email method with the
correct currently being used method.

Change-Id: I98dcc8374876e20cb5c2952121b69dab99c7cf19
Signed-off-by: Robert Lyon <robertl@catalyst.net.nz>