BUG/MEDIUM: cli: Prevent double free in CLI ACL lookup

The memory is released by cli_release_mlook, which also properly sets the
pointer to NULL. This was introduced with a big code reorganization
involving moving to the new keyword registration form in commit ad8be61c7.

This fix needs to be backported to 1.7.

Signed-off-by: Nenad Merdanovic <nmerdan@haproxy.com>

src/map.c

@@ -524,7 +524,6 @@ static int cli_io_handler_map_lookup(struct appctx *appctx)
 
 	default:
 		appctx->st2 = STAT_ST_FIN;
-		free(appctx->ctx.map.chunk.str);
 		return 1;
 	}
 }