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
(cherry picked from commit 9e5a39389c)

openstack/common/jsonutils.py

@@ -170,8 +170,8 @@ def loads(s):
     return json.loads(s)
 
 
-def load(s):
-    return json.load(s)
+def load(fp):
+    return json.load(fp)
 
 
 try: