Automatic merge from submit-queue. 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>..
Preserve leading and trailing slashes on proxy subpaths
subresource parsing was not populating path parameters correctly (leading and trailing slashes were being stripped)
this caused bad locations to be sent to the proxy, causing https://github.com/kubernetes/kubernetes/issues/52022. the first attempt to fix that (#52065) unconditionally prefixed '/', which broke the redirect case (#52813#52729)
fixes#52813, fixes#52729
needs to be picked to 1.7 and 1.8
```release-note
Restores redirect behavior for proxy subresources
```
e0f75338b5