These variables are unused since we don't use travis CI. This also allows to
remove two steps:
- 'Setup GOPATH' only printed variables
- 'Setup travis reference' modified some shell local variables that don't have
any influence on the rest of the steps
The TRAVIS var is still used by tools/osbuilder/tests to determine if
virtualization is available.
Fixes: #3544
Signed-off-by: Jeremi Piotrowski <jpiotrowski@microsoft.com>