Convert fPing tests to httpretty

Change-Id: I9e3b152e5916215c98cd218bf500f9864c763d63
blueprint: httpretty-testing
Synced jsonutils from oslo-incubator

The sync includes change that makes sure we get unicode-only dicts from
jsonutils no matter which json module implementation is selected.

The latest commit in oslo-incubator:
- 0f4586c0076183c6356eec682c8a593648125abd

Change-Id: Ic815ca3df94c33edec9104172048b2cd94b92e3f
Closes-Bug: 1314129
Merge "Convert fPing tests to httpretty"
Merge "Synced jsonutils from oslo-incubator"