Add test cases to cover IPv4 filter in IPv6 only network

This commit cover the DROPPED_IPV4_NON_DHCP4 for:
- non-UDP protocol packet
- fragmented UDP protocol packet
- UDP packet with destination port is not DHCP client

Test: atest NetworkStackTests:com.android.networkstack.android.net.apf.ApfFilterTest
Change-Id: I44a85d6f3db88bfbc0556b289e68fdabde195559
1 file changed