Split the check_status cron job into one check per tool/slice

[mtlynch]

(Migrated from code.google.com)
Reported by claudiu.perta, Jan 31, 2013
The 'check_status' cron job takes too long, sometimes causing 'Deadline exceeded' errors, so we must split this task into one check per
tool/slice.

[mtlynch]

This doesn't necessarily need to be split up into multiple tasks. We can likely do the Datastore queries more efficiently so that the processing time is not linear with the number of slices.