worker: create archive_dir before putting log file in it
worker: create archive_dir before putting log file in it

before d488b9bd, the memo for rerunning a suite is noted down by the
last-in-suite job. when the last-in-suite job is performed, the
archive_dir has been created by the jobs which performs tests, see
the `Creating archive dir` line in run_job() in teuthology/worker.py .

but after d488b9bd, the memo is logged by the first-in-suite job, by
then, none of the test jobs is performed, so their archive dirs are not
created. i think that's why the first-in-suite job fails to write the
memo to $archive_dir/results.log.

Signed-off-by: Kefu Chai <a4b264ee037c625052534d60505bfd0db4776ac4@redhat.com>

SUSE/teuthology,SUSE/teuthology,ceph/teuthology,dmick/teuthology,dmick/teuthology,ktdreyer/teuthology,SUSE/teuthology,dmick/teuthology,ktdreyer/teuthology,ceph/teuthology