Remove on_node_reset callback from volume_manager

[OpenStack Infra]

https://review.openstack.org/370643
Dear bug triager. This bug was created since a commit was marked with DOCIMPACT.

commit adaaef1eb096b936a22e11937cc8d84b9699a89a
Author: Dmitry Guryanov <email address hidden>
Date: Mon Jun 6 20:09:40 2016 +0300

    Remove on_node_reset callback from volume_manager

    Receiverd calls on_node_reset on stop deployment and
    cluster reset operations. In both cases we should preserve
    user-defined disks configuration. So remove on_node_reset
    callback which just resets disks configuration.

    DocImpact
    Change-Id: I9db43d0f0fa54ac4f4d626552b0553ee7a02ca69
    Closes-Bug: #1423328
    (cherry picked from commit 716ac3ac0af058110a7687b1c4b282fef09ab2e3)
    (cherry picked from commit fdc375b59c886a0392571dfb5ef7374e76e58243)