Fix failed test for TestRestartPolicy
Fix failed test for TestRestartPolicy

This commit is a follow up of the last commit:
Vendor engine-api to allow docker daemon reload event.

After vendor/engine-api has been updated, the following
unit test fails:
```
--- FAIL: TestRestartPolicy (0.00s)
       hostconfig_test.go:177: RestartPolicy.IsNone for { 0} should have been false but was true
```

The reason for the above failed unit test is that pull request:

https://github.com/docker/engine-api/pull/200

updated behavior of the restart policy and makes restartpolicy.IsNone
return true if restart policy name is `""`. As a result, the above
mentioned unit test fails.

This fix fixes the inconsistency of the unit test so that `TestRestartPolicy`
could pass again.

Signed-off-by: Yong Tang <765086fe2e0c1f980161f127fec596800f327f62@outlook.com>

TheBigBear/docker,TheBigBear/docker,TheBigBear/docker