Made 10 Go ports respect MAKE_ENV. This is expected to unbreak them.

Ports:
www/go-appengine-sdk devel/go-bindata devel/gogs net/rclone security/obfs4proxy-tor
misc/cryptoballot www/grafana4 sysutils/epazote net-mgmt/prometheus1 security/honeybadger

While here, corrected PYTHON_CMD in www/go-appengine-sdk/Makefile.

Approved by: tcberner (mentor, implicit)
Approved by: portmgr (port compliance, infrastructure)