Ugly workaround for what seems to be a bug in JRuby

On JRuby (9.1.15.0), if IPv6 is globally disabled on the system,
we get an EADDRINUSE with the message "Protocol family unavailable".
MRI on the other hand gives us a "Errno::EADDRNOTAVAIL" error we already properly handle.

Author: badboy

test/internals_test.rb

@@ -334,7 +334,13 @@ def af_family_supported(af)
           begin
             sa = Socket.pack_sockaddr_in(1024 + Random.rand(63076), hosts[af])
             s.bind(sa)
-          rescue Errno::EADDRINUSE
+          rescue Errno::EADDRINUSE => e
+            # On JRuby (9.1.15.0), if IPv6 is globally disabled on the system,
+            # we get an EADDRINUSE with belows message.
+            if e.message =~ /Protocol family unavailable/
+              return
+            end
+
             tries -= 1
             retry if tries > 0