build: Turn off downloading go1.5.1 for windows builds.
build: Turn off downloading go1.5.1 for windows builds.

AppVeyor service migrated Golang to default 1.5.1

harshavardhana/mc,CarterMcClellan/mc,krisis/mc,vadmeste/mc,abperiasamy/mc,balamurugana/mc,krisis/mc,minio/mc,minio/mc,vadmeste/mc,harshavardhana/mc,balamurugana/mc,CarterMcClellan/mc,abperiasamy/mc