The code in Close() that removes the watches was not working,
because it first sets `w.closed = true` and then calls w.close(),
which starts with
```
if w.closed {
return errPollerClosed
}
```
Fix by setting w.closed only after calling w.remove() for all the
files being watched.
While at it, remove the duplicated `delete(w.watches, name)` code.
Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>
(cherry picked from commit fffa8958d00860b4e3563327a2cc6836a12d4ba9)
Upstream-commit: 4e2dbfa1af48191126b0910b9463bf94d8371886
Component: engine
21c28e4566