git is required for ubuntu from source

[Yongfeng Du]

When build docker images for ubuntu/source for neutron, error occurs because of git not installed.

[Yongfeng Du (dolpherdu)]

The error msg is as follows, I see the centos source base dockerfile has git installed, so it's reasonable for ubuntu base doing the similar.
==========================
Processing /neutron
    Complete output from command python setup.py egg_info:
    ERROR:root:Error parsing
    Traceback (most recent call last):
      File "/usr/local/lib/python2.7/dist-packages/pbr/core.py", line 109, in pbr
        attrs = util.cfg_to_args(path)
      File "/usr/local/lib/python2.7/dist-packages/pbr/util.py", line 243, in cfg_to_args
        pbr.hooks.setup_hook(config)
      File "/usr/local/lib/python2.7/dist-packages/pbr/hooks/__init__.py", line 25, in setup_hook
        metadata_config.run()
      File "/usr/local/lib/python2.7/dist-packages/pbr/hooks/base.py", line 27, in run
        self.hook()
      File "/usr/local/lib/python2.7/dist-packages/pbr/hooks/metadata.py", line 26, in hook
        self.config['name'], self.config.get('version', None))
      File "/usr/local/lib/python2.7/dist-packages/pbr/packaging.py", line 640, in get_version
        raise Exception("Versioning for this project requires either an sdist"
    Exception: Versioning for this project requires either an sdist tarball, or access to an upstream git repository. Are you sure that git is installed?
    error in setup command: Error parsing /tmp/pip-iXz7EF-build/setup.cfg: Exception: Versioning for this project requires either an sdist tarball, or access to an upstream git repository. Are you sure that git is installed?

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/209331

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/209331
Committed: https://git.openstack.org/cgit/stackforge/kolla/commit/?id=12b70241badd498ed3bfda3788ea5597898e99cb
Submitter: Jenkins
Branch: master

commit 12b70241badd498ed3bfda3788ea5597898e99cb
Author: Yongfeng Du <email address hidden>
Date: Wed Aug 5 11:11:18 2015 +0800

    Install git for ubuntu source base

    git is required for installing neutron from source.

    Change-Id: I7b9b9455f8ccc1c62dba54d60846143d4bd0a1ce
    Closes-Bug: #1481560