Add module level static capabilities

The static capabilities declared in getCapabilities allows certain
capabilities to be queried before instances are created. The intended use
of this capability is to remove the need for the `is_internal_service`
function.

server/modules/authenticator/MySQLAuth/mysql_auth.c

@@ -95,6 +95,7 @@ MXS_MODULE* MXS_CREATE_MODULE()
         MXS_AUTHENTICATOR_VERSION,
         "The MySQL client to MaxScale authenticator implementation",
         "V1.1.0",
+        MXS_NO_MODULE_CAPABILITIES,
         &MyObject,
         NULL, /* Process init. */
         NULL, /* Process finish. */