TNonblockingServer can bind to port 0 (i.e., get an OS-assigned port) but there is no way to get the port number

While providing port 0 to the TNonblockingServer (C++ edition) allows the OS to assign any port that is available (this part actually works), there is no API to retrieve the port that was assigned. At least, I wasn't able to find one...

This is similar to the problem reported on THRIFT-1944.

Both TSimpleServer and TThreadedServer as of 0.9.2 have this capability.