in OSX bitbucket server can be started on port 7995 even if 127.0.0.1:7995 is already in use

macOS appears to have a different behaviour from other operating systems which results in new ServerSocket(7995) working, even if 127.0.0.1:7995 is in use. This results in failures when trying to start more than one instance of Bitbucket Server on the same macOS host because the second instance doesn't detect that the first instance has taken the default JMX port.