Unify platform_InstallTestImage with servo repair.

The body of platform_InstallTestImage was an almost verbatim copy
of SiteHost._servo_repair().  Replaced that body with a call to the
host method.

BUG=None
TEST=run_remote_tests platform_InstallTestImage

Change-Id: Ie2dc1fb2adcba544cd472f4f1052a440e21b988e
Reviewed-on: https://gerrit.chromium.org/gerrit/47389
Commit-Queue: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Richard Barnette <jrbarnette@chromium.org>
Tested-by: Richard Barnette <jrbarnette@chromium.org>
5 files changed