Refine the proto dns_resolver.proto

1. refine the enum type Transport
   The name of 1st enum value is TRANSPORT_UNKNOWN
2. remove the wrong character "CR"

Bug: 119862317
Test: ./out/host/linux-x86/bin/statsd_testdrive 116

Merged-In: Iaf7abac6170d5818a263392731069d7bf021d981
Merged-In: I8f0e7449036062ecc3827e477ced325d84c1bf54
(cherry picked from commit aee26c02)

Change-Id: Ie33a2ea58d6f39345d0f1d4141eea8b9c458dcfc