fix another lintian error and two warnings for razorqt-desktop

E: razorqt-desktop: pkg-has-shlibs-control-file-but-no-actual-shared-libs
W: razorqt-desktop: postinst-has-useless-call-to-ldconfig
W: razorqt-desktop: postrm-has-useless-call-to-ldconfig

tested with sid and quantal