Skip TestDropPacketToVpnAddress if the feature is disabled

INGRESS_TO_VPN_ADDRESS_FILTERING is disabled due to b/352424251 and
testDropPacketToVpnAddress fails if the feature is disabled.
So skip testDropPacketToVpnAddress if the feature is disabled.

Bug: 362434644
Test: adb shell device_config put tethering
      ingress_to_vpn_address_filtering -1
Test: atest CtsHostsideNetworkTests
(cherry picked from https://android-review.googlesource.com/q/commit:9d5d7d07793549a9c8a19d6277c498683cb7da3f)
Merged-In: Ib16a7550dcf93dd9ecf29047b1c4f101ff6d610d
Change-Id: Ib16a7550dcf93dd9ecf29047b1c4f101ff6d610d
4 files changed