Integrate dbus tests into the regression testing framework.

This started out as dbus-send.c, from the dbus source, and then grew
from there.

dbus_message is an example "client" program that only sends out
messages. dbus_service binds to a well-known name and then listens and
responds to incoming messages. They share some code in dbus_common.c.

The test scripts, dbus_message.sh and dbus_service.sh, share some
functionality in dbus.inc.

Signed-off-by: Tyler Hicks <tyhicks@canonical.com>
Acked-by: Seth Arnold <seth.arnold@canonical.com>