fix 'Ignore IPv6-Only Preferred option if option length is not 4'

Based on code inspection I believe
  https://android-review.git.corp.google.com/c/platform/packages/modules/NetworkStack/+/2780868
  "Ignore IPv6-Only Preferred option if option length is not 4"
is not actually enough.

Test: TreeHugger
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I0245e579fffc327a4c051f43d312d7b0167348cf
1 file changed