ART: Add JDWP trace to see how agent is attached

Tested with visual inspection of logcat following command:

adb root && \
adb shell stop && \
adb shell setprop dalvik.vm.extra-opts "-verbose:jdwp" &&\
adb shell start

Test: See above
Change-Id: I52c17f1b7b962d37d666e27abbc33b2b83fd9980
diff --git a/adbconnection/adbconnection.cc b/adbconnection/adbconnection.cc
index d0dde29..de6f6fc 100644
--- a/adbconnection/adbconnection.cc
+++ b/adbconnection/adbconnection.cc
@@ -814,8 +814,12 @@
 void AdbConnectionState::AttachJdwpAgent(art::Thread* self) {
   art::Runtime* runtime = art::Runtime::Current();
   self->AssertNoPendingException();
+
+  std::string args = MakeAgentArg();
+  VLOG(jdwp) << "Attaching JDWP agent with args '" << args << "'";
+
   runtime->AttachAgent(/* env= */ nullptr,
-                       MakeAgentArg(),
+                       args,
                        /* class_loader= */ nullptr);
   if (self->IsExceptionPending()) {
     LOG(ERROR) << "Failed to load agent " << agent_name_;