child-sa: No need to find reqid of existing trap policy

child-sa: No need to find reqid of existing trap policy

When initiating a trap policy we explicitly pass the reqid along.  I guess
the lookup was useful to get the same reqid if a trapped CHILD_SA is manually
initiated.  However, we now get the same reqid anyway if there is no
narrowing.  And if the traffic selectors do get narrowed the reqid will be
different but that shouldn't be a problem as that doesn't cause an issue with
any temporary SAs in the kernel (this is why we pass the reqid to the
triggered CHILD_SA, otherwise, no new acquire would get triggered for
traffic that doesn't match the wider trap policy).