mgm: FuseServer: caps: use a function to generate bccaps

This branch basically puts in the common functionality that is used generate the broadcast caps into a single function GetBroadcastCaps which can be called by the various broadcast refresh functions. In addition the following cleanups are done

• drop the count in favour of find, so that the iterator is reused
• make the GetTS function just call the Get() under a lock, a similar pattern is used for a TS version of GetBroadcastCaps

TODO:

• BroadcastReleasefromExternal can also be made to use this, the only addition there seems to be debug logging of mCaps.count which may be added/dropped in the GetBroadcastCaps function itself