Fix cases where we are wrapping a nil error
This was using `errors.Wrap` when there was no error to wrap, meanwhile
we are supposed to be creating a new error.
Found this while investigating some log corruption issues and
unexpectedly getting a nil reader and a nil error from `getTailReader`.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
(cherry picked from commit 0a48d26fbcb33a84da7f767c2a62cae362df9505)
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>