Adding multipath-tools package for nova hosts

[OpenStack Infra]

https://review.openstack.org/256082
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commit 232048e385da038c364615f52fc1bada6a52a48f
Author: Bjoern Teipel <email address hidden>
Date: Thu Dec 10 14:08:41 2015 -0600

    Adding multipath-tools package for nova hosts

    This fix adds the multipath-tools package to all nova
    nodes in order to support iscsi-multipath inside nova.

    In order to enable this feature in nova the following override
    needs to be configured:

    nova_nova_conf_overrides:
      libvirt:
        iscsi_use_multipath: true

    DocImpact
    Closes-Bug: #1524957

    Change-Id: I36da282043ce864c8a1fb69a1ee02e3a273c14e4