Test: Some comments and small fixes for PrivateDnsDohTest am: cdb5bbc9 am: d98324b5 am: 6133e25e am: f311d9ae am: b3afc9ab

Original change: https://android-review.googlesource.com/c/platform/packages/modules/DnsResolver/+/2447582



Change-Id: I564440aa73dbf5b53a3104814d13895d158c1e5e
Signed-off-by: Automerger Merge Worker <android-build-automerger-merge-worker@system.gserviceaccount.com>