lpm-stats: cleanup lpm stats processing sanity wrapping

during list_for_each_entry_reverse iteration, cleanup_stats
recursively on current operated stats node could result it
will be freed at the end of that cleanup_stats progress.
De-referencing it again should not happen.

CRs-Fixed: 2182622
Change-Id: Icf837b0aa796fed5fe1721f9fe66fd0dd36ccfd7
Signed-off-by: John Zhao <yuankuiz@codeaurora.org>