Default to /24 prefix for floating IP range with neutron

When running Tempest parallel tests with neutron, several long-running
tests might create routers and floating IPs, which will result in
IP allocations over the public network.

Increasing the public network size should ensure tests do not fail
due to IP address shortage; this patch also updates the public network
gateway IP address.

Related-Bug: 1253966

Change-Id: Ie075b3c4d14a07b06c42fd29b09770dd1972aa45
Merge "Default to /24 prefix for floating IP range with neutron"
XenAPI: Update DomU to Ubuntu Saucy

Driven by a race condition in LVM being hit in the tempest
tests.  This is a locking race between a file lock and a
semaphore which is fixed in 2.02.96-5.

Change-Id: I8a8c215c90a0602288292ffd06b7694d2db6219e
Fix xenapi functions' tests

The tests got outdated, this fix makes the tests pass again.

Change-Id: Iadddfbf34bf79ba455811645e766c2f3d0fcca84
Workaround missing zip snapshot

At the moment, xenserver installation depends on github snapshots.
Unfortunately, git.openstack.org does not have that capability. This
fix includes:

 - Exit with error code, if a download fails
 - create proper urls, even if they are using the git protocol
 - set git base to github - so we are able to do snapshots

Fixes bug: 1259905

Change-Id: I8d0cf8bf8abb16ee0a4b138a6719409c75e7a146