Fix wrong used ProcessExecutionError exception

This class has been moved to nova.openstack.common.processutils,
but a wrong usage is exists in nova.virt.libvirt.volume,
correct here.

Closes-bug: #1308839
Change-Id: I76f99b63dc5097b462dcff6ff63cbbb13d7580fb
Make baremetal driver use Instance object for updates

This makes the baremetal driver use the Instance object it is passed
to do its update instead of using the old conductor raw method.

Related to blueprint virt-objects-juno

Change-Id: I4116f1645562353134534dc6b883e8052c1aa706
Remove unused instance_update() method from virtapi

This removes the now-unused instance_update() method from the VirtAPI.

Related to blueprint virt-objects-juno

Change-Id: Iaa55e7156244c9cdf7558e23ecab49db162daa37
Merge "Fix wrong used ProcessExecutionError exception"
Merge "Make baremetal driver use Instance object for updates"
Merge "Remove unused instance_update() method from virtapi"