tools: Fix hanging of nfdc on wrong input

Change-Id: I4fd4fb95d3dee72f5e0b8bc2435f7fffca87e5e3
Refs: #2690

tools/nfdc.cpp

@@ -308,7 +308,7 @@ Nfdc::dispatch(const std::string& command)
     strategyChoiceUnset();
   }
   else
-    usage(m_programName);
+    return false;
 
   return true;
 }