CI: Jenkins: Use the Jenkins WORKSPACE
CI: Jenkins: Use the Jenkins WORKSPACE

Currently we place our GOPATH into our HOME dir.
This will not scale well for Jenkins slaves that are either not
oneshot/transient or run parallel builds.
Utilise the Jenkins provided WORKSPACE area for the gopath, which
also has the added benefit of potentially being cleaned up at the
end of a run.

Fixes: #667

Signed-off-by: Graham Whaley <95f36e5ac6982f4574a5c449c37cf652e934d2b9@intel.com>

devimc/tests,chavafg/tests,MarioCarrilloA/tests,clearcontainers/tests,devimc/tests,clearcontainers/tests,MarioCarrilloA/tests,chavafg/tests