xenapi: cleanup VM Installation

VM installation created a machine with multiple network interfaces. This
is a needless complexity at that point, we only need one interface. This
change removes the complex network interface setup from
install-os-vpx.sh script, so that only one network interface is created,
which is connected to the selected network (management by default). This
change also removes a lot of non-used code from install-os-vpx.sh
Specify the network to be used for ubuntu netinstall with:

    UBUNTU_INST_BRIDGE_OR_NET_NAME

defaults to $MGT_BRIDGE_OR_NET_NAME.

This change also includes:
 - use precise as default

Related to blueprint xenapi-devstack-cleanup

Change-Id: Ib0a0a316e849f2c2651305ea657c84820cd2bb3b
Enable configuration of Identity API v3

* Default IDENTITY_API_VERSION to '2.0' in stackrc

Note: the value of these *_API_VERSION variables will NOT include
the leading 'v' as the CLI tools do not allow it.

Change-Id: Ic6473833be35625282e7442f3c88fc1c4d0cc134
Set the correct URLs in the version return data

The URLs advertised in the data returned by keystone's '/' route default
to localhost and is not usable from off-host.  Not that anything in
DevStack uses it (yet).

Change-Id: I049789f568eff48c1abb0678c3ac0ae8a8960c64
Enable all notifications update from Nova for Ceilometer

This will allow Ceilometer to grab even more events about instances states
changes.

Change-Id: Ie28258607695caf96dcfa292cb74355aced85ccf
Set the scenario/img_dir option for tempest.conf

The default value does not work unless devstack is installed in
/opt/stack/new/devstack. This patch changes the img_dir option to point
to the correct install location.

Change-Id: Iea41d209dad10b2f9a7c97efd55c39a8d29347cc
Merge "Set the scenario/img_dir option for tempest.conf"
Merge "xenapi: cleanup VM Installation"
Merge "Enable configuration of Identity API v3"
Merge "Set the correct URLs in the version return data"
Merge "Enable all notifications update from Nova for Ceilometer"