Use golang from epel repo

[jarifibrahim]

See openshiftio/openshift.io#4618

With this PR, we will install golang from the website but we also support installing golang from epel (stable) repo.

[sbose78]

Build fails https://ci.centos.org/job/devtools-build-tool-detector/38/console :(

[corinnekrych]

Atm we can not build using golang v1.11 because of goa v1.3 (we need 1.4 see goadesign/goa#1548)
so +1 for proving a way of still installing manually a different version of golang than the one provided by epel-release

[alexeykazakov]

@corinnekrych you can use goa 1.3 with go 1.11. You just have to use go test -vet off when running tests.

[sbose78]

@jarifibrahim
You would need to use something like this to run the tests

go test -vet off  $(go list ./... | grep -v 'vendor\|app$\|tool\/build-tool-detector-cli\|design\|client\|test')

instead of ginkgo -r ( not sure how to set option for vet )

@corinnekrych to move to goa 1.4.0, client libraries like auth-client would also need to move to 1.4.0