test: all test_scripts should be part of tarball when building without libvirtd

test: all test_scripts should be part of tarball when building without libvirtd

Steps to reproduce this problem:
1. # ./autogen.sh --without-libvirtd
2. # make dist
3. # rpmbuild --nodeps --define "_sourcedir `pwd`" -ba libvirt.spec
   ...
   make  check-TESTS
   make[1]: Entering directory `/home/wency/rpmbuild/BUILD/libvirt-0.9.1/tests'
   make[1]: *** No rule to make target `test_conf.sh', needed by `check-TESTS'.  Stop.
   make[1]: Leaving directory `/home/wency/rpmbuild/BUILD/libvirt-0.9.1/tests'
   make: *** [check-am] Error 2
   error: Bad exit status from /var/tmp/rpm-tmp.7Rb9PV (%check)