Description of problem:

Unable to update scheduling policy from evenly_distributed to power_saving via REST API


Version-Release number of selected component (if applicable):


How reproducible:


Steps to Reproduce:
1.create DC
2.create cluster with scheduling policy 'evenly_distributed'
3.send the following command:
curl -v -u "user@domain:password" -H "Content-type: application/xml" -X PUT -d '<cluster><scheduling_policy><policy>power_saving</policy><thresholds low="20"/></scheduling_policy></cluster>' -k 'https://hostName/api/clusters/cluster_id'

Actual results:

Returns cluster info with the same scheduling policy 
<scheduling_policy href="/api/schedulingpolicies/20d25257-b4bd-4589-92a6-c4c5c5d3fd1a" id="20d25257-b4bd-4589-92a6-c4c5c5d3fd1a">
        <name>evenly_distributed</name>
        <policy>evenly_distributed</policy>
        <thresholds high="80" duration="120"/>
        <properties>
            <property>
                <name>CpuOverCommitDurationMinutes</name>
                <value>2</value>
            </property>
            <property>
                <name>HighUtilization</name>
                <value>80</value>
            </property>
        </properties>
    </scheduling_policy>


Expected results:

scheduling policy should have been updated to power_saving

Additional info: