ec2: Fix sandboxed dhclient background process cleanup.
There is a race condition where our sandboxed dhclient properly writes a
lease file but has not yet written a pid file. If the sandbox temporary
directory is torn down before the dhclient subprocess writes a pidfile
DataSourceEc2Local gets a traceback and the instance will fallback to
DataSourceEc2 in the init-network stage. This wastes boot cycles we'd
rather not spend.
Fix handling of sandboxed dhclient to wait for both pidfile and leasefile
before proceding. If either file doesn't show in 5 seconds, log a warning
and return empty lease results {}.
tests: NoCloudKVMImage do not modify the original local cache image.
The NoCloudKVMImage.execute() would modify the image in /srv/citest
that meant that after the first time you ran a test, the image was
dirty.
The change here is to make the image operate on a qcow backed image.
Also modify Snapshot to then copy the qcow rather
than creating another chained qcow. The reason being that the image
might go away or change after the snapshot has been returned.
Also
* drop use of 'override_templates' which was only relevant to LXD.
* NoCloudKVM.create_image() returned an instance before
now it has create_instance which creates an instance.
* NoCloudKVMInstance has a 'disk' attribute separate from 'name'
tests: Use apt-get to install a deb so that depends get resolved.
Instead of using 'dpkg -i' to install a package and then running
apt-get -f install, to hope that it would install needed dependencies
we can just use 'apt-get' directly to do the install.
The 'dpkg/apt-get -f' path was a problem if the installed deb was
older than the available deb. In that case it would get replaced.