In platform_InstallTestImage, don't ignore chromeos-install status

Test image installation was done with a command sequence that
meant that chromeos-install failures were ignored.  The second
command in the sequence was a redundant call to 'halt', which
was unneeded given that the test presses the power button.

BUG=chromium-os:32718
TEST=platform_InstallTestImage starting with a powered off unit

Change-Id: I1a842a61320395c9ec351827ee91b5a16f787046
Reviewed-on: https://gerrit.chromium.org/gerrit/27821
Reviewed-by: Chris Masone <cmasone@chromium.org>
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Commit-Ready: Richard Barnette <jrbarnette@chromium.org>
1 file changed