Add event logging to libpod, even display to podman

In lipod, we now log major events that occurr.  These events
can be displayed using the `podman events` command. Each
event contains:

* Type (container, image, volume, pod...)
* Status (create, rm, stop, kill, ....)
* Timestamp in RFC3339Nano format
* Name (if applicable)
* Image (if applicable)

The format of the event and the varlink endpoint are to not
be considered stable until cockpit has done its enablement.

Signed-off-by: baude <bbaude@redhat.com>

libpod/runtime_volume.go

@@ -2,9 +2,11 @@ package libpod
 
 import (
 	"context"
+	"strings"
+
+	"github.com/containers/libpod/libpod/events"
 	"github.com/pkg/errors"
 	"github.com/sirupsen/logrus"
-	"strings"
 )
 
 // Contains the public Runtime API for volumes
@@ -34,7 +36,6 @@ func (r *Runtime) RemoveVolume(ctx context.Context, v *Volume, force bool) error
 			return nil
 		}
 	}
-
 	return r.removeVolume(ctx, v, force)
 }
 
@@ -171,6 +172,7 @@ func (r *Runtime) PruneVolumes(ctx context.Context) ([]string, []error) {
 			}
 			continue
 		}
+		vol.newVolumeEvent(events.Prune)
 		prunedIDs = append(prunedIDs, vol.Name())
 	}
 	return prunedIDs, pruneErrors