Vpn test would destroy socket. If adb run over network, adb
socket would be killed during Vpn test. Then, test stop due to
adb disconnect.
Bug: 119382723
Test: - build pass
- run cts -m CtsHostsideNetworkTests -t com.android.cts.net.HostsideVpnTests
Change-Id: I91b4ab018a9e7fc73dcb7969e4a6520d6b27d629