[BUGFIX] install_golang.yml - take into account of Mac OS X checksum
[BUGFIX] install_golang.yml - take into account of Mac OS X checksum

for the `update-etc-environment.py` script, since Mac OS X doesn't seem
to have a `sha256sum` program.

Signed-off-by: Pang Yan Han <22594c345857f664c61cd411f607c4d40a9d4af9@gmail.com>

yanhan/myvagrant