Currently, openapiv3 discovery uses requestURI to discover resources.
However, that does not work when the rest endpoint contains prefixes
(e.g. `http://localhost/test-endpoint/`).
Because requestURI overwrites prefixes also in rest endpoint
(e.g. `http://localhost/openapiv3/apis/apps/v1`).
Since `absPath` keeps the prefixes in the rest endpoint,
this PR changes to absPath instead requestURI.
Kubernetes-commit: d94c733ee2bfaedd9a1c45d58fbd56c99403c94d
