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.
1 file changed