Workaround the fact that autotest tmp files may be updated during archive stage.
Workaround the fact that autotest tmp files may be updated during archive stage.

Emerging the autotest package to the factory test image while this is
running modifies the timestamp on /usr/local/autotest/server/tmp. When tar
spots this, it flags this and returns status code 1. The tarball is still
OK, although there might be a few unneeded (and garbled) tmp files. If tar
fails in a different way, it'll return an error code other than 1.

I'd rather fix this in the autotest ebuild but it's hard to see where
the problem is, so I don't know how to do that.

BUG=chromium:237537
TEST=Unit tests, remote trybot run.
Change-Id: I9d7bc241fda3dfbe0f8fdccd9be932471d8a522e
Reviewed-on: https://gerrit.chromium.org/gerrit/49930
Commit-Queue: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

bpsinc-native/src_third_party_chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,chadversary/chromiumos.chromite,bpsinc-native/src_third_party_chromite