Disconnecting volume from the compute host

cmd nova-manage volume_attachment refresh vm-id vol-id connetor

There were cases where the instance said to live in compute#1 but the
connection_info in the BDM record was for compute#2, and when the script
called `remote_volume_connection` then nova would call os-brick on
compute#1 (the wrong node) and try to detach it.

In some case os-brick would mistakenly think that the volume was
attached (because the target and lun matched an existing volume on the
host) and would try to disconnect, resulting in errors on the compute
logs.

- Added HostConflict exception
- Fixes dedent in cmd/manange.py
- Updates nova-mange doc

Closes-Bug: #2012365
Change-Id: I21109752ff1c56d3cefa58fcd36c68bf468e0a73

doc/source/cli/nova-manage.rst

@@ -1572,7 +1572,9 @@ command.
    * - 5
      - Instance state invalid (must be stopped and unlocked)
    * - 6
-     - Instance is not attached to volume
+     - Volume is not attached to the instance
+   * - 7
+     - Connector host is not correct
 
 
 Libvirt Commands