Yardstick output format unified

Yardstick output format unified

JIRA: YARDSTICK-658

Currently the yardstick have three dispatcher: file, influxdb, mongodb.
(influxdb using API to get result and mongodb using testAPI to get result)
But their output format is different. It is hard to use.

In this patch, make all dispatchers using the same data source.
And make the output format of file and influxdb unified.
As for mongodb, since it is related to testAPI, so I make it push data
every test case.

The unified output format is:
    http://paste.openstack.org/show/610125/

Change-Id: I854ac4f03e6f904469b07b0c924c7d850545ae5b
Signed-off-by: chenjiankun <chenjiankun1@huawei.com>