cros_portage_upgrade unit tests, a partial update.
cros_portage_upgrade unit tests, a partial update.

This is the first installation of a rewrite of unit tests for
cros_portage_upgrade.  This adds test targets:
EmergeableTest UtilityTest TreeInspectTest RunBoardTest

BUG=chromium-os:15426
TEST=python cros_portage_upgrade_unittest.py

Change-Id: Ifdaa1ebf77ba28af45388c1280df546369e5c862
Reviewed-on: http://gerrit.chromium.org/gerrit/10421
Commit-Ready: Matt Tennant <46e612415b446ccde19638e4035892001c237942@chromium.org>
Reviewed-by: Matt Tennant <46e612415b446ccde19638e4035892001c237942@chromium.org>
Tested-by: Matt Tennant <46e612415b446ccde19638e4035892001c237942@chromium.org>
Reviewed-by: Brian Harring <fdc2d0a2e2340b623587cee5ea8dff425d1eb1f3@chromium.org>

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