Automatic merge from submit-queue (batch tested with PRs 55908, 55829, 55293, 55653, 55665). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Use go native func after upgrading to go1.9
**What this PR does / why we need it**:
Since we have already upgraded to go1.9 (#51375), use go native func after upgrading to go1.9.
**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
ref: #52033
**Special notes for your reviewer**:
/cc @aanm @bowei
**Release note**:
```release-note
NONE
```
Automatic merge from submit-queue (batch tested with PRs 52520, 52033, 53626, 50478). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.
Removed the IPv6 prefix size limit for cluster-cidr
Fixes#50395
/sig network
/area ipv6
cc @rpothier
IPAM controller unifies handling of node pod CIDR range allocation. It
is intended to supersede the logic that is currently in range_allocator
and cloud_cidr_allocator.
Note: for this change, the other allocators still exist and are the
default.
It supports two modes:
* CIDR range allocations done within the cluster that are then
propagated out to the cloud provider.
* Cloud provider managed IPAM that is then reflected into the cluster.
