`golint` had the following issue when linting this file:
```
daemon/logger/jsonfilelog/read.go:116:10: should omit type io.Reader
from declaration of var rdr; it will be inferred from the right-hand
side
```
In order to keep it happy changing it to an indirect assignment will
still maintain the same functionality.
Signed-off-by: Tom Booth <tombooth@gmail.com>
Upstream-commit: 6314bec641b473571c0160d85bdc70250342185a
Component: engine
3b33d2d580