**What type of PR is this?**
/kind cleanup
**What this PR does / why we need it**:
Staging the GCE Cloud Provider as part of KEP [20190125-removing-in-tree-providers](https://github.com/kubernetes/enhancements/blob/master/keps/sig-cloud-provider/20190125-removing-in-tree-providers.md). Staging repo setup here https://github.com/kubernetes/legacy-cloud-providers
Moves the GCE cloud provider implementation to staging.
This is in preparation for moving the cloud provider code out of tree entirely.
However we need it in staging while the code needs to be consumed both in/out of tree.
**Which issue(s) this PR fixes**:
Fixes #
**Special notes for your reviewer**:
**Does this PR introduce a user-facing change?**:
```
NONE
```
Updated import dependency tracking.
Factored in the cleanup from #77412
Minor fix to go.mod.
This patch cleans up pkg/util/mount/* and pkg/util/volume/* to always
use filepath.Join instead of path.Join. filepath.Join is preferred
because path.Join can have issues on Windows.
This PR adds the support for GCEPD volume. For now, it uses a workaround
(https://github.com/pjh/gce-tools) to get disk number in windows for a given GCE PD name.
- Move from the old github.com/golang/glog to k8s.io/klog
- klog as explicit InitFlags() so we add them as necessary
- we update the other repositories that we vendor that made a similar
change from glog to klog
* github.com/kubernetes/repo-infra
* k8s.io/gengo/
* k8s.io/kube-openapi/
* github.com/google/cadvisor
- Entirely remove all references to glog
- Fix some tests by explicit InitFlags in their init() methods
Change-Id: I92db545ff36fcec83afe98f550c9e630098b3135
