Use $() instead of ``

There are other instances of this in other files, just tidying
ceilometer at the moment.

Change-Id: I136a20d7ac50fdf02cbd1102613e324e313b7b0a
XenAPI: Always update apt sources

If an appliance is used as a base OS, the user might want to use that in
a different region. With this change we always update the used mirrors
in the template.

Change-Id: I7a119664efac1124e54064311c243c63c2a7944b
Update the OpenDaylight support to the Helium release

The OpenDaylight project recently released their latest release, codenamed
Helium. This commit updates the devstack support for OpenDaylight to this
new version, which includes changes to configuration files as well as the
startup of OpenDaylight itself.

Also update my email address in MAINTAINERS.rst.

Change-Id: I124b5e7e8ef7feb6c90de907916a9530409c4ad4
ofagent: Support physical_interface_mappings

Also, add a knob to create a veth pair instead of a bridge
to provide host connectivity for l3-agent.  (Q_USE_PUBLIC_VETH)

Related: blueprint ofagent-physical-interface-mappings
Change-Id: I4c2538f0fd3fb05bfdb69e7e4c3a8462af42ba10
Merge "XenAPI: Always update apt sources"
Merge "Use $() instead of ``"
Merge "Update the OpenDaylight support to the Helium release"
Merge "ofagent: Support physical_interface_mappings"
Merge branch 'master' of https://github.com/openstack-dev/devstack