Enable DHCP INIT-REBOOT state on R.

Bug: 156575243
Test: atest NetworkStackTests NetworkStackIntegrationTests
Test: atest NetworkStackNextIntegrationTests
Test: manual test:
      1. connect to AP successfully at the first time
      2. disconnect wifi
      3. reconnect to the same AP
      4. checked client broadcasts REQUEST instead of DISCOVER
      5. checked client broadcasts DISCOVER if lease has expired
Change-Id: I62d1ab6b94be1ee95fbaa2ecce62eaba01e7892d