make attaching adapters more robust

to make the behavior consistent across gdb versions, ignore the initial
*stopped which gdb7 delivers while attaching.

Reviewed-By: hjk

src/plugins/debugger/gdb/trkgdbadapter.cpp

@@ -1616,6 +1616,7 @@ void TrkGdbAdapter::handleTargetRemote(const GdbResponse &record)
 {
     QTC_ASSERT(state() == InferiorStarting, qDebug() << state());
     if (record.resultClass == GdbResultDone) {
+        setState(InferiorStopped);
         emit inferiorPrepared();
     } else {
         QString msg = tr("Connecting to TRK server adapter failed:\n")