lbox_select() may leak in case of memory failure

[rtsisyk]

Both lbox_select() (Lua/C) and index:select() (FFI) may leak on a memory failure during re-allocating Lua table with results.

tarantool/src/box/lua/schema.lua

Lines 816 to 822 in 056df85

	local ret = {}
	local entry = port_buf.first
	for i=1,tonumber(port_buf.size),1 do
	ret[i] = box.tuple.bless(entry.tuple)
	entry = entry.next
	end
	builtin.port_buf_destroy(port_buf);

(see a line with call to port_buf_destroy).

A test case hard to make, however it should be possible.

[kostja]

I'm closing this since, given the tests, we're more likely to run out of finalizers first.