revamp tar-testsuite test
- simplify code by using `yum-builddep` and `rpm -i *srpm`, the
`yum deplist` doesn't seem to work on Fedora now
- run testsuite twice: by 'tar-testsuite' user and 'root' user
(running as root is important to have xattrs fully tested!)
- use `make check` instead of ./testsuite, since we need to build
genfile and other check utilities