Allow reset on internal connection state

[mp911de]

The internal state machine could run into an invalid state due to network failures, VM errors or unexpected/faulty Redis responses (i.e. version does not fit the Redis client).

This could be handled by closing the connection and reconnecting for getting a clear and defined state without any "backlog" on the TCP connection.

[mp911de]

Will add reset() method on connection impl (not connection interface!) to reset the connection state.
In case clients run into connection sync issues (can be discovered using RedisClient#addListener listening on RedisConnectionStateListener#onRedisExceptionCaught) the client can call RedisChannelHandler#reset. This might be useful especially when a SSL tunnel scrambles up the connection state and any backlog is processed by lettuce.