Found a couple of places where pretty low level errors were never being
wrapped with any sort of context.
For example, if you try to create a local volume using some bad mount
options, the kernel will return `invalid argument` when we try to mount
it at container start.
What would happen is a user would `docker run` with this volume and get
an error like `Error response from daemon: invalid argument`.
This uses github.com/pkg/errors to provide some context to the error
message without masking the original error.
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
Allows users to submit options similar to the `mount` command when
creating a volume with the `local` volume driver.
For example:
```go
$ docker volume create -d local --opt type=nfs --opt device=myNfsServer:/data --opt o=noatime,nosuid
```
Signed-off-by: Brian Goff <cpuguy83@gmail.com>
