update sysutils/terraform to 0.9.11

o update to 0.9.8 [1]
o update to 0.9.11
o switch to USES=go
o add LICENSE_FILE
o take maintainership

PR: 220166 [1]
Reported by: krion [1]
Reviewed by: swills
Approved by: swills (maintainer)
Differential Revision: https://reviews.freebsd.org/D11410