BUG/MINOR: lua: Check argument type to convert it to IP mask in arg validation

BUG/MINOR: lua: Check argument type to convert it to IP mask in arg validation

In hlua_lua2arg_check() function, before converting an argument to an IPv4 or
IPv6 mask, we must be sure to have an integer or a string argument (ARGT_SINT or
ARGT_STR).

This patch must be backported to all supported versions.

(cherry picked from commit e663a6e326c3d4d465d5aa66e4fbe3acde69aac3)
Signed-off-by: Willy Tarreau <w@1wt.eu>
(cherry picked from commit 2ef95fa486eae674cb32c491c7f5ca5da3299fee)
Signed-off-by: Willy Tarreau <w@1wt.eu>