Merge pull request #5573 from hashicorp/dani/update-vol-docs

docs: Clarify docker volume behaviour

website/source/docs/drivers/docker.html.md

@@ -259,7 +259,8 @@ The `docker` driver supports the following configuration in the job spec.  Only
   host paths to container paths. Mounting host paths outside of the allocation
   directory can be disabled on clients by setting the `docker.volumes.enabled`
   option set to false. This will limit volumes to directories that exist inside
-  the allocation directory.
+  the allocation directory. We recommend using [`mounts`](#mounts) if you wish
+  to have more control over volume definitions.
 
     ```hcl
     config {
@@ -274,10 +275,11 @@ The `docker` driver supports the following configuration in the job spec.  Only
     ```
 
 * `volume_driver` - (Optional) The name of the volume driver used to mount
-  volumes. Must be used along with `volumes`.
-  Using a `volume_driver` also allows to use `volumes` with a named volume as
-  well as absolute paths. If `docker.volumes.enabled` is false then volume
-  drivers are disallowed.
+  volumes. Must be used along with `volumes`. If `volume_driver` is omitted,
+  then relative paths will be mounted from inside the allocation dir. If a
+  `"local"` or other driver is used, then they may be named volumes instead.
+  If `docker.volumes.enabled` is false then volume drivers and paths outside the
+  allocation directory are disallowed.
 
     ```hcl
     config {