Remove findIPv4DefaultRoute

Remove unused findIPv4DefaultRoute. This allows startLegacyVpnPrivileged
to run on IPv6 and removes the "Unable to find IPv4 default gateway"
exception.

Bug: 161776767
Test: Test updated in ConnectivityServiceTest: atest FrameworksNetTests
Change-Id: Ie3e3dfdce8051dc70df704502d056645ea030245
1 file changed