Prevent IPMI actions from colliding.
Prevent IPMI actions from colliding.

Prevent IPMI actions from colliding with eachother, even if they are
issued to the API in parallel, by adding @require_exclusive_lock
decorators to public methods of the IPMIPowerDriver.

Change-Id: Ic5c12ff6a399b637eccb82c6ffd7e9c575f4edc4

faizan-barmawer/ironic-lib,NaohiroTamura/ironic-lib,openstack/ironic-lib,faizan-barmawer/elytics,citrix-openstack-build/ironic-lib