The Ironic client now supports the OSC plugin interface directly, so
this wrapper is no longer needed. Removing it will allow us to specify
which Ironic API version to use via the standard mechanisms.
Change-Id: If92855c307ecd389fbe6050e426d0ced959a9665
Depends-On: Icdbd28c487351af6d67205837aa536aedb31b41a