LUQueryInstances: keep the given order of names

Currently LUQueryInstances keeps the ordering of instances only in some cases,
and in others it will reorder the list. This patch fixes this by more clearly
separating the various cases (names passed or not and locking or not locking),
so that the output list is in the same order as always.

Of course, this disables the sorting when arguments are passed.

Reviewed-by: ultrotter