KUBE_NO_GODEPS to not use in tree godeps

If this is set, and it normally shouldn't be, the config file will not
add the in tree Godeps to the GOPATH.  So all of them must be solved by
the KUBE_EXTRA_GOPATH

hack/config-go.sh

@@ -110,8 +110,11 @@ kube::setup_go_environment() {
   if [[ -n ${KUBE_EXTRA_GOPATH:-} ]]; then
     GOPATH=${GOPATH}:${KUBE_EXTRA_GOPATH}
   fi
-  # Set GOPATH to point to the tree maintained by `godep`.
-  GOPATH="${GOPATH}:${KUBE_REPO_ROOT}/Godeps/_workspace"
+  # Append the tree maintained by `godep` to the GOPATH unless KUBE_NO_GODEPS
+  # is defined.
+  if [[ -z ${KUBE_NO_GODEPS:-} ]]; then
+    GOPATH="${GOPATH}:${KUBE_REPO_ROOT}/Godeps/_workspace"
+  fi
   export GOPATH
 
   # Unset GOBIN in case it already exists in the current session.