res_http_websockets: Fix extra unref of module

In websocket_add_protocol_internal is used to add the "echo"
protocol, but ast_websocket_remove_protocol is used to remove
it.  This causes an extra call to ast_module_unref.

ASTERISK-24480 #close
Reported by: Corey Farrell
Review: https://reviewboard.asterisk.org/r/4140/
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Merged revisions 427200 from http://svn.asterisk.org/svn/asterisk/branches/12
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Merged revisions 427201 from http://svn.asterisk.org/svn/asterisk/branches/13


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@427202 65c4cc65-6c06-0410-ace0-fbb531ad65f3

res/res_http_websocket.c

@@ -1292,7 +1292,7 @@ static int load_module(void)
 
 static int unload_module(void)
 {
-	ast_websocket_remove_protocol("echo", websocket_echo_callback);
+	websocket_remove_protocol_internal("echo", websocket_echo_callback);
 	ast_http_uri_unlink(&websocketuri);
 	ao2_ref(websocketuri.data, -1);
 	websocketuri.data = NULL;