Add support for containers.conf volume timeouts

Also, do a general cleanup of all the timeout code. Changes
include:
- Convert from int to *uint where possible. Timeouts cannot be
  negative, hence the uint change; and a timeout of 0 is valid,
  so we need a new way to detect that the user set a timeout
  (hence, pointer).
- Change name in the database to avoid conflicts between new data
  type and old one. This will cause timeouts set with 4.2.0 to be
  lost, but considering nobody is using the feature at present
  (and the lack of validation means we could have invalid,
  negative timeouts in the DB) this feels safe.
- Ensure volume plugin timeouts can only be used with volumes
  created using a plugin. Timeouts on the local driver are
  nonsensical.
- Remove the existing test, as it did not use a volume plugin.
  Write a new test that does.

The actual plumbing of the containers.conf timeout in is one line
in volume_api.go; the remainder are the above-described cleanups.

Signed-off-by: Matthew Heon <mheon@redhat.com>

libpod/volume_inspect.go

@@ -64,7 +64,12 @@ func (v *Volume) Inspect() (*define.InspectVolumeData, error) {
 	data.MountCount = v.state.MountCount
 	data.NeedsCopyUp = v.state.NeedsCopyUp
 	data.NeedsChown = v.state.NeedsChown
-	data.Timeout = v.config.Timeout
+
+	if v.config.Timeout != nil {
+		data.Timeout = *v.config.Timeout
+	} else if v.UsesVolumeDriver() {
+		data.Timeout = v.runtime.config.Engine.VolumePluginTimeout
+	}
 
 	return data, nil
 }