Fixed the set of deployed channel Ids returned by Donkey being incorrect if two channels have the same deploy date.
Issue: MIRTH-3394
Fixed channel creation failing due to a foreign key exception if multiple channels are deployed for the first time simultaneously. 

Moved the code that gets the next local channel Id into createChannel and removed getNextLocalChannelId since it was pretty pointless.

Synchronized createChannel
Issue: MIRTH-3395