Take a vm out of SNAPSHOTTING after Glance error

[OpenStack Infra]

https://review.openstack.org/76828
commit 88da0984c81fa98ff1d32915a4152773d7caa257
Author: Jan Grant <email address hidden>
Date: Wed Jan 8 12:34:07 2014 +0000

    Take a vm out of SNAPSHOTTING after Glance error

    If a snapshot is attempted to be taken when Glance can't find the
    underlying image (usually because it's been deleted), then ImageNotFound
    is raised to nova.compute.manager.ComputeManager._snapshot_instance. The
    error path for this leaves the instance in a snapshotting state; after
    which "operator intervention" is required.

    This simply reverts the instance state under that specific circumstance.

    DocImpact: previously a snapshot that failed for this reason would leave
    the instance in a spurious snapshotting task state indefinitely. Now,
    the task state is reverted. At the moment that revert is 'silent'
    (although the failure to snapshot will be evident to the user).

    Fixes-bug: #1267097
    (cherry picked from commit 96dba50737819c24b4ddd9cb1078da305638abc9)

    Conflicts:

     nova/compute/manager.py

    Change-Id: I9623cfaed31e8337ab65bc1eab85ad3b51b1a5ca

[Tom Fifield (fifieldt)]

This appears to be a welcome change in behaviour that does not need documentation