Use .cn URLs for validation on Chinese SIM cards.

Currently, when using a Chinese SIM card, network validation will
use connectivitycheck.gstatic.com. This is sometimes subject to
DNS poisoning. Use connectivitycheck.gstatic.cn instead for both
HTTP and HTTPS. The default fallback probe is already set to a
China-specific domain.

Test: m
Test: wget -O - https://connectivitycheck.gstatic.cn/generate_204
Bug: 179021745
Bug: 229934127
Change-Id: Icfb97d3b0af41d9a2c1e43286627d8612affd161
1 file changed