BinaryJedis.multi(TransactionBlock) should not call discard when exception occurred

I have found this bug from #496 (Thanks @dmk23 !)

In BinaryJedis.multi(TransactionBlock), exception normally occurred from ````results = jedisTransaction.exec()````.
(If exception occurred from jedisTransaction.execute(), I think it's up to developer - should handle to TransactionBlock.execute() block)

When exception occurred from jedisTransaction.exec(), multi() & exec() already sent to Redis, transaction ended.
So discard() has no effect, and made another error (discard without multi)

I have removed discard() from BinaryJedis.multi(TransactionBlock), and also exception handling statements.

Below is commit log

====
* In BinaryJedis.multi(TransactionBlock), multi & exec already fired before exception occured, so sending discard has no effect, and made another error
  * add unit test (error inside TransactionBlock)
    * Transaction with error - Redis discards transaction automatically (execabort)
    * Transaction with error - Redis doesn't roll back (force to execute all)