text: Title: Human readable duration formats exact year inconsistently
  Body: **What happened**:
  When the duration is **exactly** 2 years or 3 years, human readable duration is returned as `2y0d` or `3y0d`.  But when the duration is exactly 4 years, 5 years, etc, the human readable duration is returned as `4y`, `5y`, etc.
  
  **What you expected to happen**:
  The format of an exact year should be consistent.  Remove `0d` when duration is an exact year:
  * `2y0d` should be `2y`
  * `3y0d` should be `3y`
  * Check other years... 4, 5, 6, 7... not sure if they also have the problem.
  
  **How to reproduce it (as minimally and precisely as possible)**:
  Because this is time-dependent, it can be difficult to reproduce via the CLI, but you can see the problem illustrated in [this unit test](https://github.com/kubernetes/kubernetes/blob/15bb54c2d2c515ad155b90c2c2ca59eaa1cd3f65/staging/src/k8s.io/apimachinery/pkg/util/duration/duration_test.go#L77) which shows the current behavior:
  ```
  		{d: 2 * 365 * 24 * time.Hour, want: "2y0d"},
  		{d: 2*365*24*time.Hour + 23*time.Hour, want: "2y0d"},
  		{d: 3 * 365 * 24 * time.Hour, want: "3y0d"},
  		{d: 8*365*24*time.Hour - time.Millisecond, want: "7y364d"},
  		{d: 8 * 365 * 24 * time.Hour, want: "8y"},
  		{d: 8*365*24*time.Hour + 364*24*time.Hour, want: "8y"},
  		{d: 9 * 365 * 24 * time.Hour, want: "9y"},
  ```
  
  The `2y0d` and `3y0d` test cases should be changed to want `2y` and `3y`, and the code should be changed to make that pass.
  
  **Anything else we need to know?**:
  Note, this is not a problem when the duration is exactly 1 year because the human readable duration is still shown in days.  So nothing needs to change to handle the case of exactly 1 year.
  
  **Environment**:
  - Kubernetes version (use `kubectl version`):  1.18
  - Cloud provider or hardware configuration:  n/a
  - OS (e.g: `cat /etc/os-release`):  n/a
  - Kernel (e.g. `uname -a`):  n/a
  - Install tools:  n/a
  - Network plugin and version (if this is a network-related bug):  n/a
  - Others:  n/a
  