WL-3156 Meeting location is not ignored

Pulled in commit from central to fix this. I always thought his fix was a lot hackier than mine but in practice the caching that happens in the central `SignupMeetingBean` is unreliable.

It turned out that because the JSF page had conditional rendering, there was also conditional form validation. When the method was called outside of the normal execution path the caching broke somehow...

By calling the cache that exists with in the `NewSignupMeetingBean` specifically, we make sure that any magical JSF calls to `isAllLocationsEmpty` fire off correctly.

:octopus: