WL-2599 When we have a problem with LDAP throw error.

Basically we should be throwing serious problems with LDAP back up the stack so that we don't mask problems. This caused an issue where groups were returned as empty when LDAP became unavailable and this caused site groups to have members removed from them. The LDAP became available again the groups memberships didn't reappear.
Merge pull request #1 from ox-it/WL-2599

WL-2599 When we have a problem with LDAP throw error.