Reorganize dbus interface builds

The previous structure is failing meson scan-build. Reorganize it to
follow the example in hothd and it will now build and pass the
scan-build.

Google-Bug-Id: 375055000
Change-Id: Icfdf023c78818f2499294642cf25c2be5cdb9378
Signed-off-by: Willy Tu <wltu@google.com>
18 files changed