Actually disable collision-protect in parallel_emerge.
Actually disable collision-protect in parallel_emerge.

I tried to disable parallel_emerge yesterday, but my change didn't work,
so the buildbots are still running into occasional related issues.

Portage has two flags for doing collision protection: collision-protect
and protect-owned. The protect-owned feature is enabled by default and
is quite useful: it checks to make sure that we don't have multiple
packages that own the same file. The collision-protect feature is more
strict, and less useful: it fails if it finds a conflicting file, even
if that file was created by an earlier ebuild that failed to install.

We want to disable collision-protect here because we don't handle
failures during the merge step very well -- we just leave the old
Unfortunately, we haven't quite figure out the best way to handle
these failures in parallel emerge, so for now we disable the flag.

TEST=Created a fake collision, made sure that packages still merge.
BUG=none

Review URL: http://codereview.chromium.org/2825076

vmware/coreos-scripts,sigma/coreos-scripts,mjg59/scripts,fivethreeo/scripts,fivethreeo/scripts,andrejro/coreos--scripts,zhang0137/scripts,mischief/scripts,nicescale/scripts,marineam/coreos-scripts,vmware/coreos-scripts,gtank/scripts,trnubo/scripts,nicescale/scripts,glevand/coreos--scripts,BugRoger/scripts,vmware/coreos-scripts,fivethreeo/scripts,endocode/scripts,BugRoger/scripts,smilart/scripts,gtank/scripts,smilart/scripts,trnubo/scripts,coreos/scripts,crawford/scripts,crawford/scripts,bcwaldon/coreos-scripts,coreos/scripts,mischief/scripts,BugRoger/scripts,bcwaldon/coreos-scripts,mjg59/scripts,andrejro/coreos--scripts,marineam/coreos-scripts,andrejro/coreos--scripts,crawford/scripts,sigma/coreos-scripts,zhang0137/scripts,marineam/coreos-scripts,gtank/scripts,mischief/scripts,glevand/coreos--scripts,trnubo/scripts,nicescale/scripts,sigma/coreos-scripts,smilart/scripts,mjg59/scripts,bcwaldon/coreos-scripts,endocode/scripts,zhang0137/scripts,endocode/scripts