Re-allow the "Run" menuitem after target exited

	* src/persp/dbgperspective/nmv-dbg-perspective.cc
	(DBGPerspective::init_actions): Move the RunMenuItemAction into
	the inferior_loaded_action_group.
	(DBGPerspective::update_action_group_sensitivity): Do not disallow
	the sensitivity of the inferior_loaded_action_group after the
	target exited.