Call the runfabtests script with the full path, rather than cd'ing
into the fabtests directory. This only matters because the
runfabtests script tries to write temporary files into '.', and
sometime we may be testing from a fabtests directory that is build
by some other user.
@jshimek
Signed-off-by: Sung-Eun Choi sungeunchoi@users.noreply.github.com