Don't install autotest bits to the image.
Don't install autotest bits to the image.

Autotest installs stuff to the image via ssh, so there's no need to include
all of this stuff to the image. This saves disk space. Note that
/usr/local/autotest-chrome is currently already excluded from the image
because of a hack in the chrome ebuild, and that /usr/local/autotest is
usually also excluded from the image because autotest is not included
as a dependency of any packages that are installed.

In the factory setting, it looks like the factory has its own code for
installing autotests via rsync. Presumbably, if the factory tests are
managing the autotest directly, they won't want emerge mucking with the
directory as well on the image. Currently, emerge doesn't muck with the same
directory, but we probably want to ensure that it doesn't start doing that in
future to ensure sanity.

TEST=Built images. Modded for factory test. Verified that (a) build directory contains autotests, (b) regular images do not contain autotests; and (c) images modified for factory test do contain autotests

Review URL: http://codereview.chromium.org/3124010

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