Razor packages must not overwrite git deployments

The general opinion of the community was that installing packages over the top
of an existing git deployment of Razor is a bad idea, and they should refuse
to install.

I tend to agree: that is the most conservative approach, and puts the
responsibility on the end user to decide how they want to handle the
change over.

This shouldn't last forever, but we should at least initially have pre-install
and pre-upgrade code that refuses to install if /opt/razor/.git exists.

This implements that using pre-install scripts to check for the git directory
being present - but only for the first install; upgrades ignore it, so that
managing configuration through git will work after that first install is
pushed through.

This closes #322.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Use fully-qualified VM hostname for internal tests

Using a fully-qualified VM hostname makes it much easier to run acceptance
tests over a remote network through the VPN - in turn, reducing friction when
it comes to building new acceptance tests.

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Test packages refuse to install over git deployments

This adds an acceptance test to verify that we don't install packages over the
top of an existing git deployment.  This should help ensure that our
preinstall scripts actually work to abort in that case.

In the words of Knuth, "Beware of bugs in the above code; I have only proved
it correct, not tried it." -- in this case, I have verified it as far as I am
able, but limitations of internal package repositories, multiple Jenkins
deployments, and branch testing mean that I am unfortunately unable to run
this through a full CI suite in the real world.

Consequently I expect something to blow up when faced with reality, although
it should only be a minor deviation in the road.  (None of this is helped, of
course, by bugs in other products that make it harder to verify success or
failure than I might like.)

Signed-off-by: Daniel Pittman <daniel@rimspace.net>
Merge pull request #322 from daniel-pittman/feature/master/322-refuse-to-install-over-git-deployments

Ensure that the Razor packages will not install over an existing git-based deployment.