Exclude the latency in DnsStats if it is relevant to EPERM

The latency from permission error should not be counted because
there is no real DNS packet sent out. This will help us see a more
correct server latency in DNS statistics.

Bug: 188153519
Test: cd packages/modules/DnsResolver && atest
Change-Id: Id4d4f422421daf71680ce87ea345b0e494bd71fc