upgrades: Handle upgrade interval other than 1 day properly
upgrades: Handle upgrade interval other than 1 day properly

- We must assume that apart from Plinth there will be user or user-agent
  changes to the configuration files.  In this case the value may be set
  something other than '1' day.

harry-7/Plinth,kkampardi/Plinth,kkampardi/Plinth,kkampardi/Plinth,vignanl/Plinth,vignanl/Plinth,jvalleroy/plinth-debian,vignanl/Plinth,freedomboxtwh/Plinth,harry-7/Plinth,vignanl/Plinth,jvalleroy/plinth-debian,freedomboxtwh/Plinth,freedomboxtwh/Plinth,freedomboxtwh/Plinth,kkampardi/Plinth,jvalleroy/plinth-debian,harry-7/Plinth,jvalleroy/plinth-debian,freedomboxtwh/Plinth,jvalleroy/plinth-debian,vignanl/Plinth,kkampardi/Plinth,harry-7/Plinth,harry-7/Plinth