Check for both new and old shflags during stateful update
Check for both new and old shflags during stateful update

BUG=chromium-os:21966
TEST=perform an update from an old build that doesn't have dev-util/shflags
installed to a current tot build

Change-Id: I999e49f658b99302b591450bf3c3788181408a91
Reviewed-on: http://gerrit.chromium.org/gerrit/10533
Reviewed-by: Doug Anderson <49983c4a76b998672954ed5edf4a62db4a336502@chromium.org>
Tested-by: Sonny Rao <d867fc987a366be56684d1145622524a3ba1efbf@chromium.org>

coreos/dev-util,mgireesh05/dev-util,mgireesh05/dev-util,marineam/coreos-dev-util,marineam/coreos-dev-util,mgireesh05/dev-util,coreos/dev-util,coreos/dev-util