Tell teuthology to use a local ceph-qa-suite directory

By default teuthology will clone the ceph-qa-suite repository and use the tasks it contains. If tasks have been modified localy, teuthology can be instructed to use a local directory by inserting something like:

suite_path: /home/loic/software/ceph/ceph-qa-suite

in the teuthology job yaml file. The directory must then be added to the PYTHONPATH

PYTHONPATH=/home/loic/software/ceph/ceph-qa-suite \
   ./virtualenv/bin/teuthology  --owner \
   /tmp/work.yaml targets.yaml