driver-list command to show the list of conductors

The commit https://review.openstack.org/#/c/60216/ returns the name of the
drivers and also a list of active conductors that supports each driver,
this patch makes the necessary changes to expose that information on
the driver-list command.

Change-Id: I9183b40422f6dc3193570703d25d47b6e8edde06
Merge "driver-list command to show the list of conductors"