[tests/cannon] Remove a lot of useless printing in cannon, use barrier instead of sleep.
[tests/cannon] Remove a lot of useless printing in cannon, use barrier instead of sleep.

fhijaz/Graphite,victorisildur/Graphite,victorisildur/Graphite,mit-carbon/Graphite-Cycle-Level,victorisildur/Graphite,mit-carbon/Graphite-Cycle-Level,8l/Graphite,fhijaz/Graphite,mit-carbon/Graphite,mit-carbon/Graphite,mit-carbon/Graphite,8l/Graphite,fhijaz/Graphite,8l/Graphite,nkawahara/Graphite,nkawahara/Graphite,victorisildur/Graphite,mit-carbon/Graphite-Cycle-Level,mit-carbon/Graphite-Cycle-Level,nkawahara/Graphite,8l/Graphite,nkawahara/Graphite,mit-carbon/Graphite,fhijaz/Graphite