Synced jsonutils from oslo-incubator

The sync includes change that drastically enhances performance on Python
2.6 with fresh simplejson library installed.

The latest commit in oslo-incubator:
- 732bdb6297eb9de81667f7713ebcb1ccc2ee45a7

Change-Id: Ib3dc0b713ed90396919feba018772243b3b9c90f
Closes-Bug: 1314129
Fix client fixtures

Some of the client fixtures used for testing were invalid. v2
tokens must have 'access'/'token'/'expires', and v3 tokens must
have 'token'/'expires_at'.

Change-Id: I2614c7deed47c9758c2031418110108308634296
Related-Bug: #1174499
Merge "Synced jsonutils from oslo-incubator"