jsonutils.load() accepts file pointer, not string

Renamed jsonutils.load() argument name to more appropriate one. This
name is also used in stdlib json documentation [1].

1: https://docs.python.org/2/library/json.html#json.load

Change-Id: Ia0cfce0e023ce29d3aad80a71039343643820bb4
Merge "jsonutils.load() accepts file pointer, not string"