Make heal_instance_info_cache_interval clearer

[Romain Hardouin]

The nova.conf documentation is generated from Nova sources.

When an operator reads nova.conf configuration options it's not obvious that heal_instance_info_cache_interval is an instance network related information.

The current description for heal_instance_info_cache_interval is:

    Number of seconds between instance info_cache self healing updates

It should be clear that this setting will update instance network information.
Moreover "info_cache" is an implementation detail. It's not relevant for operators.

[OpenStack Infra (hudson-openstack)]

Fix proposed to branch: master
Review: https://review.openstack.org/163897

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/163897
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=63da3bf5bd7ccbfe237bd56bbf13e007460ad39f
Submitter: Jenkins
Branch: master

commit 63da3bf5bd7ccbfe237bd56bbf13e007460ad39f
Author: Romain Hardouin <email address hidden>
Date: Thu Mar 12 17:17:31 2015 +0100

    heal_instance_info_cache_interval help clearer

    nova.conf documentation is auto generated from nova sources.
    It should be clear that this setting will update instance network
    information.

    Change-Id: If0f1cf57aeb68e30982381f4597e55f393cbc026
    Closes-Bug: #1431438