Use consistent hash type in Berksfile

This change uses consistent hash types in the Berksfile. Before
there were two different assignments:
  cookbook "statsd",
    :git => "git://github.com/att-cloud/cookbook-statsd.git"
  cookbook "openstack-common",
    git: "git://github.com/stackforge/cookbook-openstack-common.git"

This fixes that issue so they are both consistent.

Change-Id: Id20e2249b1f00a4abd90639243e4a1e600a64c47