Update network preference priority value for VPN

Currently netd supports only the default value for VPN but CS
send priorty value 1 to netd. It will break the default routing
for VPN. Thus, update network preference priority value to 0 for
VPN.

Bug: 193245476
Test: atest CtsHostsideNetworkTests:HostsideVpnTests
Change-Id: I197cb358e8e30355fbf675e4c623abebe7abdb7f
1 file changed