Book/Cal backends - do not call g_propagate_error() when there is no error

It only printed a runtime warning on a console
Recurring events not shown on Exchange 2010 servers

The Exchange 2010 servers are more strict with respect of recurring
events, they require also PidLidAppointmentTimeZoneDefinitionRecur
property, and claim an error (MESSAGE_CORRUPT) when saving recurring
blobs with missing Reserve2 parts.