ARMband patches for the fuel@opnfv deploy scripts

ARMband patches for the fuel@opnfv deploy scripts

These are a collection of patches that adapt the current Fuel deploy
scripts for mainly two purposes:

  - Make it possible to create a Fuel VM on a remote libvirt server.
    We use the LIBVIRT_DEFAULT_URI environment variable to detect that.
    Local deploys are possible by setting this variable to
    'quemu:///system', or leaving it empty.
    See: https://libvirt.org/remote.html for more details.

  - Make it possible to add additional network interfaces. For this we
    allow the user to pass the "-b bridge" paramter several times, and
    creating a new virtual NIC for each of them, in the same order they
    were given.
    This required a bit of refactoring of the code.

None of the changes above should break backwards compatibility, except
when indicated in the commit (search for CHANGE in the log)

In addition there are some updates to the code that were deemed
necessary, like the ability to retry when executing shell commands
instead of directly failing, and a simplification of the DHA IPMI
adapter.

Change-Id: I8a0cd5b8672383decd861309328137971eaed14b
Signed-off-by: Josep Puigdemont <josep.puigdemont@enea.com>