[#858] run_tests.py print usage if zero args
[#858] run_tests.py print usage if zero args

janiheikkinen/irods,PaulVanSchayck/irods,janiheikkinen/irods,PaulVanSchayck/irods,janiheikkinen/irods,PaulVanSchayck/irods,PaulVanSchayck/irods,janiheikkinen/irods,janiheikkinen/irods,janiheikkinen/irods,PaulVanSchayck/irods,PaulVanSchayck/irods,PaulVanSchayck/irods,PaulVanSchayck/irods,janiheikkinen/irods,janiheikkinen/irods,janiheikkinen/irods,PaulVanSchayck/irods