Move listener parameter handling into Listener::create

The Listener::create method now takes a set of configuration parameters
from which it constructs a listener. This removes the duplicated code and
makes the behavior of listener creation similar to other objects in
MaxScale. It also allows the configuration parameters to be stored in the
listener object itself.

server/core/server.cc

@@ -197,7 +197,7 @@ Server* Server::server_alloc(const char* name, MXS_CONFIG_PARAMETER* params)
 
     SSL_LISTENER* ssl = NULL;
 
-    if (!config_create_ssl(name, params, false, &ssl))
+    if (!config_create_ssl(name, *params, false, &ssl))
     {
         MXS_ERROR("Unable to initialize SSL for server '%s'", name);
         return NULL;