Add test result dispatcher

Add test result dispatcher

This patch is the initial implementation of DB result storage.

Having implemented a dispathcer which enable user select different ways
to store test results according to different requirements. This patch
can support not only local file storage, but also remote storage by
using http request(it will call common-db-api when available). Later,
local DB sotrage will be supported.

This patch is raw and simple, which is implemented with reference to
openstack ceilometer.

Any comment is welcome.

JIRA: YARDSTICK-61

Change-Id: Icaf8369edfab5d05f0819eb02d5b05dc8a04d69d
Signed-off-by: QiLiang <liangqi1@huawei.com>