Remove getHasDns() and VirtualNetwork.mHasDns

getHasDns() and VirtualNetwork.mHasDns are no more useful after commit
aops/658122.

Bug: 116539103
Test: system/netd/tests/runtests.sh pass

Change-Id: Ica04984a954a9e89a5eb38a9b262775d686f8ed4
diff --git a/server/NetdNativeService.cpp b/server/NetdNativeService.cpp
index 3331438..f9a83e4 100644
--- a/server/NetdNativeService.cpp
+++ b/server/NetdNativeService.cpp
@@ -349,9 +349,11 @@
     return statusFromErrcode(ret);
 }
 
-binder::Status NetdNativeService::networkCreateVpn(int32_t netId, bool hasDns, bool secure) {
+binder::Status NetdNativeService::networkCreateVpn(int32_t netId, bool secure) {
     ENFORCE_PERMISSION(CONNECTIVITY_INTERNAL);
-    int ret = gCtls->netCtrl.createVirtualNetwork(netId, hasDns, secure);
+    auto entry = gLog.newEntry().prettyFunction(__PRETTY_FUNCTION__).args(netId, secure);
+    int ret = gCtls->netCtrl.createVirtualNetwork(netId, secure);
+    gLog.log(entry.returns(ret).withAutomaticDuration());
     return statusFromErrcode(ret);
 }