oeqa/selftest/devtool: Ensure dbus is built befoe running test

If dbus isn't build first the dbus dependency of dbus-wait can't be detected
through pkgconfig and the test fails:

AssertionError: {'DEPENDS': {'dbus'}} != {}
- {'DEPENDS': {'dbus'}}
+ {} : Some expected variables not found in recipe: {'DEPENDS': {'dbus'}}

Ensure dbus is built and present in the sysroot.

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Signed-off-by: Armin Kuster <akuster808@gmail.com>