Add test for IPv4 UDP forwarding rules in BPF map

Parse the dumpsys output strings to check that the IPv4 UDP
forwarding rule is added by the UDP conntrack event on
the tethering interface.

Test: atest EthernetTetheringTest
Change-Id: I2f04af72e51ca6b7a37ba51daa4f5125cb11144c
2 files changed