install hook sets openstack-origin to grizzly for precise

[Ryan Beisner]

Install hook sets openstack-origin to grizzly for precise, causing install hook to fail with:

## ceilometer-agent juju unit log:
2015-06-26 16:17:36 INFO install The following packages have unmet dependencies:
2015-06-26 16:17:36 INFO install python-ceilometer : Depends: python-sqlalchemy (< 0.8) but 0.8.4-1build1~cloud0 is to be installed
2015-06-26 16:17:37 INFO install E: Unable to correct problems, you have held broken packages.
2015-06-26 16:17:37 INFO install Traceback (most recent call last):
2015-06-26 16:17:37 INFO install File "/var/lib/juju/agents/unit-ceilometer-agent-0/charm/hooks/install", line 89, in <module>
ssh-keygen -f "/home/ubuntu/.ssh/known_hosts" -R 10.245.162.1012015-06-26 16:17:37 INFO install hooks.execute(sys.argv)
2015-06-26 16:17:37 INFO install File "/var/lib/juju/agents/unit-ceilometer-agent-0/charm/hooks/charmhelpers/core/hookenv.py", line 557, in execute
2015-06-26 16:17:37 INFO install self._hooks[hook_name]()
2015-06-26 16:17:37 INFO install File "/var/lib/juju/agents/unit-ceilometer-agent-0/charm/hooks/install", line 48, in install
2015-06-26 16:17:37 INFO install fatal=True)
2015-06-26 16:17:37 INFO install File "/var/lib/juju/agents/unit-ceilometer-agent-0/charm/hooks/charmhelpers/fetch/__init__.py", line 183, in apt_install
2015-06-26 16:17:37 INFO install _run_apt_command(cmd, fatal)
2015-06-26 16:17:37 INFO install File "/var/lib/juju/agents/unit-ceilometer-agent-0/charm/hooks/charmhelpers/fetch/__init__.py", line 428, in _run_apt_command
2015-06-26 16:17:37 INFO install result = subprocess.check_call(cmd, env=env)
2015-06-26 16:17:37 INFO install File "/usr/lib/python2.7/subprocess.py", line 511, in check_call
2015-06-26 16:17:37 INFO install raise CalledProcessError(retcode, cmd)
2015-06-26 16:17:37 INFO install subprocess.CalledProcessError: Command '['apt-get', '--assume-yes', '--option=Dpkg::Options::=--force-confold', 'install', 'python-ceilometer', 'ceilometer-common', 'ceilometer-agent-compute']' returned non-zero exit status 100
2015-06-26 16:17:37 ERROR juju.worker.uniter.operation runhook.go:107 hook "install" failed: exit status 1

## apt source list on ceilometer-agent (nova-compute) unit
ubuntu@juju-beis0-machine-5:/etc/apt/sources.list.d$ cat cloud-archive.list
deb http://ubuntu-cloud.archive.canonical.com/ubuntu precise-updates/grizzly main

ubuntu@juju-beis0-machine-5:/etc/apt/sources.list.d$ cat cloud_config_sources.list
deb http://ubuntu-cloud.archive.canonical.com/ubuntu precise-updates/cloud-tools main

This was discovered while adding amulet functional tests to the ceilometer-agent/next charm.