Revert "net: nexthop: release IPv6 per-cpu dsts when replacing a nexthop group"

This reverts commit 26ed13d0 which is
commit 1005f19b upstream.

This is not needed for Android systems and is part of a patch series
that breaks the abi, so revert it.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: Id328fa580aef11e281542d0bda5d4f74861a98b4