Typo fix: Fix 'archive_dir' is not defined error.
Typo fix: Fix 'archive_dir' is not defined error.

BUG=none
TEST=Run unit tests.
TBR=build breaker

Change-Id: Icac3401799c5bdc0364ad185edcae50cc10a396e
Reviewed-on: http://gerrit.chromium.org/gerrit/4514
Tested-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>
Reviewed-by: David James <f231dc574bbeb62604660cbc162d1b8642a0a3af@chromium.org>

chadversary/chromiumos.chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,coreos/chromite,zhang0137/chromite,bpsinc-native/src_third_party_chromite,zhang0137/chromite,coreos/chromite,bpsinc-native/src_third_party_chromite,chadversary/chromiumos.chromite,coreos/chromite