systemd: fix ptest to make it able to run on target
This patch mainly involves four changes.
1. Ship the sys.tar.xz and extract it on target to avoid ELOOP error.
2. Make systemd-ptest rdepend on bash and perl as the test cases need them.
3. Fix paths in Makefile so that the test cases could run on target.
4. Install ${libdir}/udev/rules.d directory to make udev-test.pl work.
