Cleanup OpsController::get_node_info.
REST API fail to authenticate with Ldap

With AD enabled, always getting a 401 in REST API
for non admin even though user credentials properly bind
with AD.

https://bugzilla.redhat.com/show_bug.cgi?id=1146110
Merge pull request #696 from abellotti/rest_api_ldap_authentication

REST API fail to authenticate with Ldap
Merge pull request #634 from martinpovolny/ops_get_node_info

Cleanup OpsController::get_node_info.
return empty list for resource pool without host or parent cluster

This is to address the following error:

Error caught: [NoMethodError] undefined method `collect' for nil:NilClass
vmdb/app/models/resource_pool.rb:165:in `all_host_ids'
vmdb/app/models/mixins/aggregation_mixin.rb:95:in `aggregate_hardware'
vmdb/app/models/mixins/aggregation_mixin.rb:28:in `aggregate_cpu_speed'
...

showing for resource pools, which -- for whatever reason -- do not
have a host or a parent cluster.

https://bugzilla.redhat.com/show_bug.cgi?id=1133569