Make dbus monitor policies machine specific

Policy configurations will be loaded by machine within the system meta
layer (in this case meta-witherspoon). This allows different machines to
have different policies and/or different policy configurations.

The .bbappend can be used to alter which policies are used on a machine.
The thought here being that most machines within the same system meta
layer would use the same policies. However these policies would likely
have different configurations, this is where each machine would have its
own policy configuration which would be loaded per the policy recipe.

Tested:
    Built witherspoon phosphor-dbus-monitor resulting in no image change
    Built swift phosphor-dbus-monitor where no polices exist now

Change-Id: Icf187d8dafad8b10eea603c783cebcdace6e174d
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
11 files changed