util: no-op NetworkMonitor on unsupported platforms

NetworkMonitor::getCapabilities() function reports what functions
and signals are supported on current platform.

refs #4025

Change-Id: I2c2825e0f9919a734fb78b4699a483c837ee09af
diff --git a/tests/integrated/network-monitor.cpp b/tests/integrated/network-monitor.cpp
index 3b4a516..ac74862 100644
--- a/tests/integrated/network-monitor.cpp
+++ b/tests/integrated/network-monitor.cpp
@@ -55,6 +55,8 @@
   boost::asio::io_service io;
   NetworkMonitor monitor(io);
 
+  std::cout << "capabilities=" << monitor.getCapabilities() << std::endl;
+
   monitor.onNetworkStateChanged.connect([] {
     logEvent() << "onNetworkStateChanged" << std::endl;
   });