Made 14 Go ports respect MAKE_ENV. This is expected to unbreak them.

Ports:
www/fabio benchmarks/bombardier www/go-www net-mgmt/prometheus2 sysutils/immortal
sysutils/docker-freebsd audio/pms-devel sysutils/consul-alerts net-mgmt/pushgateway net/nsq
textproc/jid net-mgmt/alertmanager sysutils/nomad security/ssh-vault

Approved by: portmgr (port compliance, infrastructure)