On some networks, telephony may teardown its network
(unregisterAfterReplacement) when wifi is toggled to change the MMS
capability.
Update testRejectUnvalidated_TearDownNetwork to take that into account:
right after toggling wifi to make it unvalidated, wifi may still be
default if mobile data is being reconnected. Wait for mobile data to
reconnect and validate in that case.
Bug: 296403855
Test: atest
Change-Id: Ief46bed41ecb23d75c9a1f58e7a272e7f3de7caf
c19e8a00cc