database: cast float and time types in incrementalCounter.
database: cast float and time types in incrementalCounter.

Newer Redis version requires arguments types to be string or integer.

Change-Id: I5f3fba9affda3b0747372da824ca0662cc95a495
Reviewed-on: https://go-review.googlesource.com/78535
Reviewed-by: Ross Light <dfccc06f14414bff5a59be7fc90abf4404b47fc8@google.com>

golang/gddo,golang/gddo,segmentio/gddo,golang/gddo,segmentio/gddo,golang/gddo,segmentio/gddo,segmentio/gddo