Send empty LinkProperties when entering StoppedState.

Additionally, no longer try to transition from within a State's
enter() method (this can encounter Log.wtf()s). Introduce some
CMD_JUMP_* commands and use deferMessage().

Test: as follows
    - built
    - flashed
    - booted
    - runtest frameworks-net passes (except for IpConnectivityMetricsTest failures)
    - manual changing from DHCP to static configurations works:
  2017-12-11T19:06:19.082 - INVOKE onLinkPropertiesChange({{InterfaceName: wlan0 LinkAddresses: []  Routes: [] DnsAddresses: [] Domains: null MTU: 0}})

Bug: 69800563
Bug: 70394432
Change-Id: Ice249a48b66806c0270ec3f11dd2e8e387d4e29b