Turn off ec2_ephemeralswap for now
This script broke around FreeBSD 11.0 as a result of SWAPMETA no longer
being reported by vmstat -z; but it also needs to be reworked due to the
arrival in EC2 of nvme ephemeral disks.
I'll turn this option back on after I've found time to rewrite the
script in question.
Reported by: meta@
MFC after: 1 week