BUG/MINOR: httpclient/lua: don't pop the lua stack when getting headers

hlua_httpclient_table_to_hdrs() does a lua_pop(L, 1) at the end of the
function, this is supposed to be done in the caller and it is already be
done in hlua_httpclient_send().

This call has the consequence of poping the next parameter of the
httpclient, ignoring it.

This patch fixes the issue by removing the lua_pop(L, 1).

Must be backported in 2.5.

src/hlua.c

@@ -7097,7 +7097,6 @@ struct http_hdr *hlua_httpclient_table_to_hdrs(lua_State *L)
 	}
 
 skip_headers:
-	lua_pop(L, 1);
 
 	return result;
 }