Change unit of duration params to hours to align it with duration config at...

Change unit of duration params to hours to align it with duration config at other places in Loki (#998)

* Change unit of duration params to hours to align it with duration config at other places in Loki

other configurations like periodic table duration, retention are set in hours so this change makes
duration config for backup tool consistent and easy to manage configurations

* update parent docker image for bigtable backup tool