[release-branch.go1.26] internal/poll: readWriteUnlock should destroy fd when no remaining references
Updates #77404
Fixes #77405
Change-Id: I0402becb94855baf942d6ba3815cc2a3c1526d6e
Reviewed-on: https://go-review.googlesource.com/c/go/+/740921
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
(cherry picked from commit
31c9bcb1037a332fd547808693cd1899090b5854)
Reviewed-on: https://go-review.googlesource.com/c/go/+/741360
Auto-Submit: Michael Pratt <mpratt@google.com>