Remove WifiEntry usage of hidden connectivity API

RouteInfo.isIPv4Default is a hidden symbol, the supported way to check
the same is to use isDefaultRoute, and verify that the address is IPv4.

Bug: 182859030
Test: m WifiTrackerLib
Merged-In: Iba2efd80623e01d22a37980f2c7453cdac37b562

Change-Id: Ia9c6a5e27e6166264a65af4075f1697521542e8c
1 file changed