Resolve potential deadlocks in BungeeServerInfo.

http://www.spigotmc.org/threads/players-getting-read-timed-out-yourkit-finds-deadlock-at-senddata.27771/ is a report of a deadlock in sendData.

Upon some quick examination, I found inconsistent use of synchronization in sendData(), which may be causing issues. This commit fixes the inconsistent application of synchronization.

I have confirmed with the reporter of the issue that the patch has helped them solve the issue.