Fix node-redis createCluster normalized client

[stijnveenman]

Background

When using node-redis, a client can be created using createClient and createCluster. When createCluster is used, scanIterator is not part of the cluster client, and cannot be called from the root. This caused our TTL not to be set, as isRedis would be false, which would cause the redis-io arguments to be used.

Next to that, if scanIterator would be called with the current implementation when using a cluster, it would crash. As neither the io-redis implementation nor the scanIterator can be used.

Fix

We also set isRedis to true when "masters" in client, which can be used to check whether createCluster was used.
This fixed the mget and set behaviour, as now the correct node-redis implementation is used.

This does not fix scanIterator yet, as this cannot be called from the root. redis/node-redis#2657
So this also adds a custom implementation that calls scanIterator on each node of the cluster, and yiels all keys from each node.

[wavded]

Thx for working on this @stijnveenman , can you fix up the formatting, then I think it's ready to go.

[stijnveenman]

@wavded should be fixed now