Fix setting rpath on different targets

One one hand, libgvfsdaemon.so hasn't rpath set, which is necessary because it depends on libgvfscommon.so that is installed outside of the default library directory (look #411 (closed)).

On the other hand, executable monitor targets are setting rpath but it's not necessary for them because they don't depend on libgvfsdaemon.so or libgvfscommon.so.