Remove Mock class monkey patching

Replace use of Mock with Mock(). The Mock class was being modified and
so affecting other tests where Mock is used. An instance of the Mock
class is now used to keep the tests isolated.

Change-Id: Iccab8430d5814258c8c2d1f9af015bce999549bc
Closes-Bug: #1286245
Remove module timeutils

Change-Id: I1e548f7dcbb06f7f47f08fc475bb1fe6713b538a
Convert the DateTime into ISO8601 format for Ceilometer

The fields of DateTime type should be converted to the time in
ISO8601 format, when they are put in the usage information to be
reported to Ceilometer.

Change-Id: I67e9e3609291d0d835156dfd9cfda88deae119c1
closes-bug: #1372791
Merge "Remove module timeutils"
Merge "Convert the DateTime into ISO8601 format for Ceilometer"
Merge "Remove Mock class monkey patching"