commands_map broken after switch to redis ~4

[kzemek]

redis-rb 4 introduced a breaking change in version 4.0 where redis.client became a CLIENT command to Redis server. This breaks commands_map that sets values on redis.client.command_map, but probably also the whole subscribe_stop function.

An easy fix is to just replace redis.client with redis._client, as I've done here: path-network@fb7e374

According to the redis-rb changelog for 4.0.1 the proper way to replace client usage is to use a new redis.connection function instead.

[kares]

Thanks for the report, we pushed 3.6.1 please let us know if you run into any issues.
In the fix we tried to avoid using the 'internal' _client unless necessary: #86 ... but otherwise it started based on your suggestions.