Update to fix for Bug 6302.
There is no need to check block constraints as min length already guarantees this, this also fixes false positives for missing TOS metric blocks

Change-Id: Icbe3067d2506fad1c7dbcb175d932a5f242fa5cd
Signed-off-by: Anish Bhatt <anish@chelsio.com>
Reviewed-on: https://code.wireshark.org/review/2995
Reviewed-by: Anders Broman <a.broman58@gmail.com>