Fix Freeseer#647 Skip tests related to RMTP plugin for Windows

Partly fix Freeseer#647.
The RMTP plugin is not included in GStreamer for Win32, so the test based on it can cause problems.
This fix will skip these tests.

src/freeseer/tests/framework/test_plugins.py

@@ -89,6 +89,9 @@ def plugin_platform_category_cache():
 def test_plugin_bin(plugin_manager, plugin_info, expected_instance):
     """Check that a plugin and its get method returns the proper gst.Bin object"""
     plugin_name, get_plugin_method = plugin_info
+    if get_plugin_method == 'get_output_bin' and sys.platform == 'win32':
+        # Skip the RMTP plugin test case because it does not support win32 platform
+        pytest.skip()
     plugins = plugin_manager.get_plugins_of_category(plugin_name)
 
     for plugin in plugins: