Qt4: Use correct qdbus executable in macro.

Commit v3.0.0-rc1~71^2~9 (Qt4: Use IMPORTED executable names with
custom commands., 2014-01-24) erroneusly changed this command to
use the wrong target.
Merge topic 'fix-Qt4-DBus-macro' into next

fc2bad57 Qt4: Use correct qdbus executable in macro.