The syscall package is locked down and the comment in [1] advises to
switch code to use the corresponding package from golang.org/x/sys. Do
so and replace usage of package syscall with package
golang.org/x/sys/unix where applicable.
[1] https://github.com/golang/go/blob/master/src/syscall/syscall.go#L21-L24
This will also allow to get updates and fixes for syscall wrappers
without having to use a new go version.
Errno, Signal and SysProcAttr aren't changed as they haven't been
implemented in /x/sys/. Stat_t from syscall is used if standard library
packages (e.g. os) require it. syscall.SIGTERM is used for
cross-platform files.
Remove kubectl's dependence on pkg/api/helper, as part of
broader effort to isolate kubectl from the rest of k8s.
In this case, the code becomes private to kubectl; nobody else uses it.
**Which issue this PR fixes**
Part of a series of PRs to address kubernetes/community#598
**Special notes for your reviewer**:
**Release note**:
```release-note
NONE
```