Add podman container cleanup to CLI

When we run containers in detach mode, nothing cleans up the network stack or
the mount points.  This patch will tell conmon to execute the cleanup code when
the container exits.

It can also be called to attempt to cleanup previously running containers.

Signed-off-by: Daniel J Walsh <dwalsh@redhat.com>

Closes: #942
Approved by: mheon

libpod/options.go

@@ -485,6 +485,18 @@ func WithIDMappings(idmappings storage.IDMappingOptions) CtrCreateOption {
 	}
 }
 
+// WithExitCommand sets the ExitCommand for the container, appending on the ctr.ID() to the end
+func WithExitCommand(exitCommand []string) CtrCreateOption {
+	return func(ctr *Container) error {
+		if ctr.valid {
+			return ErrCtrFinalized
+		}
+
+		ctr.config.ExitCommand = append(exitCommand, ctr.ID())
+		return nil
+	}
+}
+
 // WithIPCNSFrom indicates the the container should join the IPC namespace of
 // the given container.
 // If the container has joined a pod, it can only join the namespaces of