Bug 1178240 - Make OAuthLoaderMixin.load check for empty job collections
Bug 1178240 - Make OAuthLoaderMixin.load check for empty job collections

If th_collections is empty, don't call th_publisher's
post_treeherder_collections(), since it won't have anything to post.
Whilst post_treeherder_collections() will do nothing in this case (since
the th_collections loop will be a no-op), it still wastes time
initialising the client.

adusca/treeherder,adusca/treeherder,KWierso/treeherder,tojon/treeherder,moijes12/treeherder,akhileshpillai/treeherder,wlach/treeherder,vaishalitekale/treeherder,parkouss/treeherder,KWierso/treeherder,parkouss/treeherder,sylvestre/treeherder,kapy2010/treeherder,wlach/treeherder,moijes12/treeherder,gbrmachado/treeherder,rail/treeherder,rail/treeherder,KWierso/treeherder,moijes12/treeherder,KWierso/treeherder,moijes12/treeherder,tojonmz/treeherder,akhileshpillai/treeherder,edmorley/treeherder,gbrmachado/treeherder,gbrmachado/treeherder,wlach/treeherder,kapy2010/treeherder,sylvestre/treeherder,adusca/treeherder,vaishalitekale/treeherder,avih/treeherder,deathping1994/treeherder,tojonmz/treeherder,avih/treeherder,jgraham/treeherder,tojonmz/treeherder,wlach/treeherder,rail/treeherder,jgraham/treeherder,parkouss/treeherder,jgraham/treeherder,deathping1994/treeherder,akhileshpillai/treeherder,rail/treeherder,moijes12/treeherder,tojonmz/treeherder,glenn124f/treeherder,wlach/treeherder,adusca/treeherder,tojon/treeherder,adusca/treeherder,glenn124f/treeherder,sylvestre/treeherder,vaishalitekale/treeherder,jgraham/treeherder,parkouss/treeherder,rail/treeherder,sylvestre/treeherder,edmorley/treeherder,tojon/treeherder,gbrmachado/treeherder,avih/treeherder,akhileshpillai/treeherder,vaishalitekale/treeherder,edmorley/treeherder,parkouss/treeherder,deathping1994/treeherder,avih/treeherder,glenn124f/treeherder,tojonmz/treeherder,rail/treeherder,kapy2010/treeherder,adusca/treeherder,glenn124f/treeherder,glenn124f/treeherder,tojon/treeherder,edmorley/treeherder,avih/treeherder,moijes12/treeherder,parkouss/treeherder,akhileshpillai/treeherder,glenn124f/treeherder,jgraham/treeherder,vaishalitekale/treeherder,avih/treeherder,wlach/treeherder,gbrmachado/treeherder,akhileshpillai/treeherder,sylvestre/treeherder,vaishalitekale/treeherder,jgraham/treeherder,gbrmachado/treeherder,deathping1994/treeherder,kapy2010/treeherder,tojonmz/treeherder,kapy2010/treeherder,sylvestre/treeherder,deathping1994/treeherder,deathping1994/treeherder