Bug 1049626 - Only allow gear move between districted nodes
Rationale:
districted to non-districted nodes not allowed: gear uids on non-districted nodes may not be in the range of uids supported by the district
between non-districted nodes not allowed:: gear uids are not set in mongo and we can not guarantee same uid for both source and destination
Bug 1056178 - Add useful error message during node removal from district