BUG/MINOR: lua: Ignore the reserve to know if a channel is full or not

The Lua function Channel.is_full() should not take care of the reserve because
it is not called from a producer (an applet for instance). From an action, it is
allowed to overwrite the buffer reserve.

This patch should be backported as far as 1.7. But it must be adapted for 1.8
and lower because there is no HTX on these versions.

(cherry picked from commit 0ec740eaee5b919b7d568daf251c8ce218143639)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 99471972da9d7516165adb8c104771ef8219fbb1)
Signed-off-by: Willy Tarreau <w@1wt.eu>
diff --git a/src/hlua.c b/src/hlua.c
index 5f5b2c3..a2dde4b 100644
--- a/src/hlua.c
+++ b/src/hlua.c
@@ -3213,22 +3213,13 @@
 __LJMP static int hlua_channel_is_full(lua_State *L)
 {
 	struct channel *chn;
-	int rem;
 
 	MAY_LJMP(check_args(L, 1, "is_full"));
 	chn = MAY_LJMP(hlua_checkchannel(L, 1));
-
-	if (IS_HTX_STRM(chn_strm(chn))) {
-		struct htx *htx = htxbuf(&chn->buf);
-
-		rem = htx_free_data_space(htx);
-	}
-	else
-		rem = b_room(&chn->buf);
-
-	rem -= global.tune.maxrewrite; /* Rewrite reserved size */
-
-	lua_pushboolean(L, rem <= 0);
+	/* ignore the reserve, we are not on a producer side (ie in an
+	 * applet).
+	 */
+	lua_pushboolean(L, channel_full(chn, 0));
 	return 1;
 }