Remove redundant module checks and references.

This removes references that are no longer needed due to automatic
references created by module dependencies.

In addition this removes most calls to ast_module_check as they were
checking modules which are listed as dependencies.

Change-Id: I332a6e8383d4c72c8e89d988a184ab8320c4872e

funcs/func_periodic_hook.c

@@ -486,11 +486,6 @@ static int load_module(void)
 
 	res = ast_custom_function_register_escalating(&hook_function, AST_CFE_BOTH);
 
-	if (!res) {
-		/* For Optional API. */
-		ast_module_shutdown_ref(AST_MODULE_SELF);
-	}
-
 	return res ? AST_MODULE_LOAD_DECLINE : AST_MODULE_LOAD_SUCCESS;
 }