An admin-api extension to show pool info was supported at commit
https://review.openstack.org/#/c/119938/.
This change adds a command to show pool information for backends
using the admin-api. This change also closes the gap for end users.
Partial-Bug: 1403902
Change-Id: I20e0828c5403b73bc44d07eebf08e2aa2deb428a