CLEANUP: lua: control executed twice

The availaible size in the stack is check two times. This patch removes
this double check.

Must be backported in 1.6
diff --git a/src/hlua.c b/src/hlua.c
index 5a1785d..deff4cc 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -5378,11 +5378,6 @@
 				RESET_SAFE_LJMP(stream->hlua.T);
 				return 0;
 			}
-			if (!lua_checkstack(stream->hlua.T, 1)) {
-				SEND_ERR(smp->px, "Lua sample-fetch '%s': full stack.\n", fcn->name);
-				RESET_SAFE_LJMP(stream->hlua.T);
-				return 0;
-			}
 			hlua_arg2lua(stream->hlua.T, arg_p);
 			stream->hlua.nargs++;
 		}