Allow configuration of periodic task interval

The redis job queue supports delayed jobs but it only checks for them
once every 10 pops or once every five minutes.  This is fine in production
but when running integration tests we want faster turn around time.  This
allows us to force the periodic task execution to one second in integration
tests which speeds them up substantially but leave the standard periodic
time calculation in production which is optimized for lower load.

Change-Id: I74cf3ca78660bd1ae7c1c88c278a15b4a56f6064
Merge "Allow configuration of periodic task interval"