### Description

At the moment db_redis driver does not support interfacing with a redis cluster. This is a proposal to add support to it. The db_redis module will get a new module parameter to enable cluster support (with default 0 - disabled):

``` modparam("db_redis", "cluster", 1) ```

The redis url used by other modules needs to specify all nodes in the cluster, and must NOT include redis database number (since it's not supported in cluster mode):

``` #!define DBURL_USRLOC "redis://10.0.1.1:6379,10.0.1.2:6379,10.0.1.3:6379" ```

The implementation is going to use the [hiredis-cluster](https://github.com/Nordix/hiredis-cluster) library (BSD license). If cluster mode is not enabled the module will behave like before, i.e. all calls to redis will use hiredis library directly.

If you find this proposal sensible, I'll start coding it.

Feedback is welcome, of course!