Bug 1276030 - Somewhat simplify the polling logic for new jobs
Bug 1276030 - Somewhat simplify the polling logic for new jobs

This also fixes a minor bug where fetching older jobs could result
in some updates being re-fetched needlessly.

edmorley/treeherder,KWierso/treeherder,edmorley/treeherder,kapy2010/treeherder,tojon/treeherder,tojonmz/treeherder,glenn124f/treeherder,tojon/treeherder,KWierso/treeherder,tojon/treeherder,edmorley/treeherder,kapy2010/treeherder,tojonmz/treeherder,KWierso/treeherder,tojonmz/treeherder,kapy2010/treeherder,tojonmz/treeherder,tojonmz/treeherder,kapy2010/treeherder,akhileshpillai/treeherder,glenn124f/treeherder,glenn124f/treeherder,akhileshpillai/treeherder,tojon/treeherder,KWierso/treeherder,kapy2010/treeherder,akhileshpillai/treeherder,akhileshpillai/treeherder,tojonmz/treeherder,akhileshpillai/treeherder,glenn124f/treeherder,glenn124f/treeherder,akhileshpillai/treeherder,glenn124f/treeherder,edmorley/treeherder