Tempest benchmark context should accept user specified tempest.conf file

[Rohan]

As of commit (f109e72cedc8797634208edd0e64e40fa599eb1d), Rally does not allow users to specify their own tempest.conf file from the Tempest scenario task.

Rally should allow user to specify his own Tempest configuration with the Tempest Scenario task

Update:
In addition to above feature, The "rally-manage tempest" should have subcommand "config-set" to allow users to specify their own Tempest config

And also have subcommand "config-gen" to allow user to auto generate Tempest config.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/128336

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/128336
Committed: https://git.openstack.org/cgit/stackforge/rally/commit/?id=dde561addbf0546d86ad8631148d624b50abedbd
Submitter: Jenkins
Branch: master

commit dde561addbf0546d86ad8631148d624b50abedbd
Author: Rohan Kanade <email address hidden>
Date: Tue Oct 14 17:29:03 2014 +0200

    Allow user specified tempest.conf

    * Allow user specified tempest.conf in tempest benchmark tasks

    Change-Id: I2591aa2febef3313cfcf0060566d17349d5da5ac
    Closes-Bug: #1369407