Mention the new way to specify hosts where instances are launched.
Compare with these two ways.
Also fixed a few things in the existing docs:
1. Fixed the policy rule name for forced_host.
2. Updated the "openstack availability zone list" command to use the
--compute option.
3. Replaced the "openstack host list" example with
"openstack compute service list --service nova-compute"
since the os-hosts API was deprecated in 2.43.
Depends-On: https://review.opendev.org/#/c/669609/
Part of Blueprint: add-host-and-hypervisor-hostname-flag-to-create-server
Change-Id: Ic471c0621e15aa497d33ef010c7f87890508fbeb
zhu.boxiang
fd480a7a3d