zeroconf/Avahi: move dbus_shutdown() call to the end of Main()

Calling dbus_shutdown() too early will break the "udisks2" neighbor
plugin.

Makefile.am

@@ -46,6 +46,7 @@ src_mpd_LDADD = \
 	$(STORAGE_LIBS) \
 	$(PLAYLIST_LIBS) \
 	$(AVAHI_LIBS) \
+	$(DBUS_LIBS) \
 	$(LIBWRAP_LDFLAGS) \
 	$(SQLITE_LIBS) \
 	$(DECODER_LIBS) \
@@ -67,6 +68,8 @@ src_mpd_LDADD = \
 	libutil.a \
 	$(SYSTEMD_DAEMON_LIBS)
 
+src_mpd_CPPFLAGS = $(AM_CPPFLAGS) $(DBUS_CFLAGS)
+
 src_mpd_SOURCES = \
 	src/Main.cxx src/Main.hxx