WL-3116 Get an up-to-date list of locations

When adding a new meeting, the SignupMeetingsBean can still exist but might
not have updated the flags for existance of categories or locations.

The recent patch[1] for WL-2926 causes the locations and categories to be
cached, so we can just call the local methods `getAllLocations()` etc.

[1] https://github.com/ox-it/wl-signup/pull/27
WL-3116 Do not count select instruction in lists

When determining whether the list of locations or categories is empty, do
not use the UI version of the list which will always include the default
option which is something like 'select a location'.

This uses the method from the `SignupMeetingsBean` instead which, mercifully,
is also cached.
Merge pull request #28 from ox-it/WL-3116

WL-3116 Get an up-to-date list of locations