net-mgmt/p5-OSLV-Monitor: Update to 1.0.4

Also add p5-JSON-XS - it really does improve the speed when the
system is under high load.

This version also implements an exclude feature. For me, that
skips monitoring of short running jails, such as those started
by poudriere.

re: https://github.com/VVelox/OSLV-Monitor/releases/tag/1.0.4