Unify log tag of DNS resolver

Set LOG_TAG to "resolv" on DNS resolver. Then, the log can be filtered
by "adb logcat [filterspecs]", such as "adb logcat *:S resolv:*", or
'grep'.

Test: resolv_integration_test pass
Change-Id: Ic4f97685d487257560ec3dfe62bab0d187bf9d93
diff --git a/DnsTlsSessionCache.cpp b/DnsTlsSessionCache.cpp
index 8d6dc6b..8e379c1 100644
--- a/DnsTlsSessionCache.cpp
+++ b/DnsTlsSessionCache.cpp
@@ -16,7 +16,7 @@
 
 #include "DnsTlsSessionCache.h"
 
-#define LOG_TAG "DnsTlsSessionCache"
+#define LOG_TAG "resolv"
 //#define LOG_NDEBUG 0
 
 #include "log/log.h"