Add support for SCAN command

Also fix invalid expire error for SET since we now test on 2.8.17.
https://github.com/antirez/redis/commit/a6edfceaa876ac6f21d7995aaf2380ab0eb50cbe

Change-Id: I838f6979e402f8f81c5ef2556b219a6f80adcc0c
Reviewed-on: http://gerrit.causes.com/44281
Reviewed-by: Shane da Silva <shane.dasilva@brigade.com>
Tested-by: Shane da Silva <shane.dasilva@brigade.com>