Fix build on Gerrit master

Change number and patch-set number are int on Gerrit
master. We need to convert into string when we evaluate as
generic properties to be used in the its-base rules.

This I9e4c8bffa change, changed Change.Id from string to int.

Change-Id: Ieec098eca84d52209d87fba8cff33cd51f8bc3aa