Implement ansible driver

Implement ansible driver

- According to inputs parameters, setup test environment. If failed
during setupping, qtip will exited. If successful, execute metric
tests.
- Parameters(optional):
	* keypair: the keypair to login/execute commands to the remote
	  hosts. They can be automatically generated.
	* hostfile: a inventory file. If not give, it can be
	  automatically generated via installer.
	* args: the parameters passed to playbook
- Use ansible python api to trigger ansible-playbook.

Unit test will be in a new patch.

Change-Id: I7470d348308f7cb6cb669bcc49063cf0f4da2111
Signed-off-by: wu.zhihui <wu.zhihui1@zte.com.cn>