Reapply "netfilter: conntrack: allow sctp hearbeat after connection re-use"

This reverts commit 35452319 as it
causes merge conflicts with 5.4.258.  It will be added back after the
merge.

Change-Id: I8ea66985ba95de649890adacc26670d01cee6d52
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>