Skip res_doh_send() if there is no validated DoH servers am: 9b748ee3 am:...

Skip res_doh_send() if there is no validated DoH servers am: 9b748ee3 am: 8570d545 am: 9d3928b1 am: a014d63c

Original change: https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/1936191

Change-Id: Ic2d93fa025e42725b44ff55e6b178ff346f817d9