1. make TEST_DIR configurable, and configure it to ptest dir, since
the *.service for test are installed into ptest dir.
2. always follow symbolic links in SOURCE when copy test files
to install dir, since some *.service under test dir are linked to
../unit/*.service which are not installed into ptest dir
Signed-off-by: Roy Li <rongqing.li@windriver.com> Signed-off-by: Ross Burton <ross.burton@intel.com>
