This also removes the rw_checkout var as it's not longer changes the affect of whether we use the ssh url or not.
Note that this replaces the other CL from last night because the other CL didn't work. The other CL still pulled in the same manifest that has http: url's for each git repo. I reverted that change last night after I noticed this.
Change-Id: I3d4ad2be6887ac2cf4ed2009bad9cae6dfdf5bbf
BUG=chromium-os:9509
TEST=Ran with cbuildbot --clobber and incremental
Review URL: http://codereview.chromium.org/5278010
TEST=Ran script and re-ran cbuildbot to completion of sync.
Change-Id: I31fddca6f720fecb461a96c1ffa54d4923b3c1c4
Review URL: http://codereview.chromium.org/3166019