Disable accept_ra upon IPv6 default route has gone for dual-stack devices.

Disabling IPv6 stack completely when IPv6 provisioning loss happens
due to the default route has gone might introduce other issues, kernel
will drop the IPv6 packets on the non-IPv6 capable interface which is
used in the wifi calling. Instead just disable accept_ra parameter,
assure upcoming RA packets won't be processed on the specific interface,
then there is only IPv4 provisioning and IPv6 link-local info left.

Bug: 179222860
Test: atest NetworkStackIntegratioTest
Change-Id: I03cfe4fd74e6e7c46ae62b73563fb4cd28392bfc