BUG/MEDIUM: hlua: Properly detect shudowns for TCP applets based on the new API

BUG/MEDIUM: hlua: Properly detect shudowns for TCP applets based on the new API

The internal function responsible to receive data for TCP applets with
internal buffers is buggy. Indeed, for these applets, the buffer API is used
to get data. So there is no tests on the SE to properly detect connection
shutdowns. So, it must be performed by hand after the call to b_getblk_nc().

This patch must be backported as far as 3.0.

(cherry picked from commit c64781c2c8b307fba7499fc70102d4246e850240)
Signed-off-by: Christopher Faulet <cfaulet@haproxy.com>