Simplify network settings for cluster VMs

[Dmitry Mescheryakov]

Right now Savanna expects cluster VMs to have two IP addresses: internal and another auto-assigned floating one. Also user needs to provide network name, which in fact is not needed. Cluster nodes access each other via hostnames and Savanna configures them via their public IPs

Change the behaviour in the following way: do not ask user for network name, just grab the first one in the list if there are several of them. Also allow user to select two modes:
1. Cluster VMs have only internal IPs. These IPs should be used both for inter-cluster communication and by Savanna.
2. The same as now.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/25900

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/25900
Committed: http://github.com/stackforge/savanna/commit/75affe206e4c3f42197581533cbca42b16a40748
Submitter: Jenkins
Branch: master

commit 75affe206e4c3f42197581533cbca42b16a40748
Author: Dmitry Mescheryakov <email address hidden>
Date: Tue Apr 2 16:35:02 2013 +0400

    Introduced new networking option for cluster

    Now Savanna can provision cluster without floating IPs. Also removed 'apt-get install xsltproc' crutch from the setup script

    Change-Id: I9240fe7402a398f5642823d87edc2408129eec2d
    Fixes: bug #1163226