added ability to lookup tasks by schedule id
889893 - added detection of still queued scheduled calls and skip re-enqueueing with log message
moved the update_next_run from the end of the run to the beginning
some formatting and comments to make the code clearer
added unit tests for new functionality
Merge pull request #248 from pulp/jconnor-889893-scheduled-sync-collisions-pulp-2.0

Jconnor 889893 scheduled sync collisions master