Consolidate get_*nodes* functions

[aeva black]

http://git.openstack.org/cgit/openstack/ironic/tree/ironic/db/sqlalchemy/api.py?id=3af35b4093a07eb2a36a4493b0ff863aa95d3fed#n184

There are currently 5 separate methods to get a node or list of nodes, based on some filter paramter, which return a node object. There's one method (get_nodeinfo_list) which is much more flexible and returns a dict of fields, but takes many filter parameters and covers the same functionality as the other 5 methods.

We should consolidate the following methods into something more maintainable and flexible.
- get_node
- get_node_list
- get_nodeinfo_list
- get_node_by_instance
- get_associated_nodes
- get_unassociated_nodes
- get_nodes_by_chassis

[Michael Davies (mrda)]

This bug has has significant overlap with the implementation of bug/1260099 (refer https://review.openstack.org/#/c/63937/7), so should be considered as part of that fix.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/63937
Committed: https://git.openstack.org/cgit/openstack/ironic/commit/?id=487f6738bcb331115b49a88f21520b412cdcc49c
Submitter: Jenkins
Branch: master

commit 487f6738bcb331115b49a88f21520b412cdcc49c
Author: Yuriy Zveryanskyy <email address hidden>
Date: Tue Dec 24 15:41:54 2013 +0200

    Add parameter for filtering nodes by maintenance mode

    Boolean parameter 'maintenance' added to API for filtering
    nodes by maintenance mode, example:
    /nodes?maintenance=false
    strutils.bool_from_string() used for converting 'associated'
    and 'maintenance' parameters, accepted values now for True
    ('1', 't', 'true', 'on', 'y', 'yes'), for False
    ('0', 'f', 'false', 'off', 'n', 'no') case-insensitive.
    Refactored dbapi method get_node_list with filters used for
    _get_nodes_collection in nodes controller.

    Partial-Bug: #1260099
    Partial-Bug: #1271291
    Change-Id: I01a62eb641316e890d191cf569bb3cf00b7619f2