Move /xapi/* -> /xenops/* in XenStore

It's really xenops that's using these paths so it makes sense that these paths
be under that name.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
CP-6172: Add VBD.other_config:backend-kind

Note: this change is co-dependent on a change in xenopsd.

Blktap3 and kernel blkback need to co-exist and, since kernel blkback watches
keys in the /local/domain/0/vbd/ tree, the paths for blktap3 need to be moved.

A new key has been added to the other_config field of the VBD record which is
passed through to xenopsd to determine where to place the VBD's XenStore
entries.

Signed-off-by: Si Beaumont <simon.beaumont@citrix.com>
Merge pull request #1496 from simonjbeaumont/xenops-xenstore-paths

Move /xapi/* -> /xenops/* in XenStore
xe-toolstack-restart: Handle xenopsd proliferation, and only restart enabled services

We now have multiple xenopsd processes for different backend libraries.
The restart script needs to handle this, restarting only the variant
that is supposed to be running.

This change is more general, and only restarts any Xapi-related process
if chkconfig says that it should be running.

Signed-off-by: Euan Harris <euan.harris@citrix.com>
Merge pull request #1555 from euanh/ea1268

xe-toolstack-restart: Handle xenopsd proliferation, and only restart ena...
Merge pull request #1512 from simonjbeaumont/cp-6172-xapi-part

Add VBD.other_config:backend-kind for blktap3