vzlist: fix PRINT_STR_FIELD

It was broken by commit b199f80. A negative value was passed
so p_outbuffer was decremented rather than incremented.

Before this patch, vzlist could not show fields that go after
any of those for which we use PRINT_STR_FIELD.

Signed-off-by: Kir Kolyshkin <kir@openvz.org>
1 file changed