BinaryShardedJedis.disconnect() may occur memory leak

Scenario:
When the middle node of cluster goes down, BinaryShardedJedis.disconnect() will unable to release connections of the following nodes, this causes memory leak.

Solution:
Ignore the exception node, so that all other normal nodes can release all connections.

This pull request adds a unit test for this solution.
Thanks to @marcosnils's guide.
Sorry, I didn't see the comment in the main thread. Let me try some stuff to check why isBroken doesn't work in travis.