Add support for cluster reset command. 

Some tests were refactored per the inclusion of the new command.

You may check cluster reset functionality in the link below:

https://github.com/antirez/redis-doc/blob/9f29c553bd083d645ac5960e17b5c118bac1e882/topics/cluster-spec.md#nodes-reset
We can remove unused ocal variables nodes and node1Id l.