ironic: use instance object for plug_vifs

It will be better if we'll use `instance` like object.

Change-Id: I8af1afc8eb7feafae25e6f14045528d2ceb74cbd
ironic: use instance object for `rebuild`

It will be better if we'll use `instance` like object.

Change-Id: Ib713357bd55ed5db27dbfd1c657479bd2ed5e90d
ironic: use instance object for `get_info`

It will be better if we'll use `instance` like object.

Change-Id: I9e465c1eba9347c2f0ae686de7476b2f0c5bb17f
ironic: use instance object for `_wait_for_active`

It will be better if we'll use `instance` like object.

Change-Id: I9e263cd4f94f25c3902a98e1471f8d093d0b2030
ironic: use instance object for `_add_driver_fields`

It will be better if we'll use `instance` like object.

Change-Id: I81099563a8f76577c2b5c6901d2b0b89b86182a2
Merge "ironic: use instance object for plug_vifs"
Merge "ironic: use instance object for `rebuild`"
Merge "ironic: use instance object for `get_info`"
Merge "ironic: use instance object for `_wait_for_active`"
Merge "ironic: use instance object for `_add_driver_fields`"