Adapt Yardstick to copy yardstick.conf to /etc/yardstick

Adapt Yardstick to copy yardstick.conf to /etc/yardstick

JIRA: DOVETAIL-466

1. Yardstick danube.3.1 needs a yardstick.conf file in /etc/yardstick
2. Copy the file /home/opnfv/repos/yardstick/etc/yardstick/yardstick.conf.sample
   to /etc/yardstick/yardstick.conf
3. If user wants to store the results in the local file, set the dispatcher to
   be 'file'.
4. If user wants to push the results into the DB, set the dispatcher to be 'http'
   and target to be the api url getting from the user.

Change-Id: I39c30883b471ab7cb29ed6d63ba8c232da39c135
Signed-off-by: xudan <xudan16@huawei.com>