EthernetTetheringTest: reduce test upstream prefix range

Change upstream address prefix range from "10.0.0.0/8" to
"10.0.0.1/24" for reducing the flaky rate which caused by the
downstream address prefix conflict with upstream address.
Especially, "10.0.0.0/8" is one of downstream address prefix
range candidate. See PrivateAddressCoordinator.

Bug: 243314243
Change-Id: If995f1d20ac52b84757ac3dec198cae1ebb7e272
Test: atest EthernetTetheringTest
1 file changed