contrib/install-autotest-server.sh: add steps for installing git

So that the autotest source code tree can be fetched and the other
packages installed via `autotest-install-packages-deps`.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
contrib/install-autotest-server.sh: use autotest-install-packages-deps

Revert back to the previous way of installing server package deps.
With the separate step that installs git this now works when the
user has the install script only, and not a checked out tree.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
contrib/install-autotest-server.sh: use `ip` instead of `ifconfig`

When attempting to detect the IP address that the Autotest server
will be listening on.

Signed-off-by: Cleber Rosa <crosa@redhat.com>
frontend/pkgdeps.py: remove non-existing ubuntu package

Signed-off-by: Cleber Rosa <crosa@redhat.com>