Description of problem:
When executing measurement_utils.js, collection interval will not be changed when using interval method.

Version-Release number of selected component (if applicable):
JON 3.1.0 
JON 3.1.1

How reproducible:
always

Steps to Reproduce:
1. log in to the JON CLI;
2. from the JON CLI command line execute the following:

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exec -f /home/JON_311/util.js
exec -f /home/JON_311/measurement_utils.js

mm = new MeasurementModule();

interval = mm.interval;
time = mm.time;
updates = { context: 'Resource', id: 24171, schedules: {'Free Memory': interval(30, time.minutes)}};
mm.updateSchedules(updates);
  
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3. Navigate to JON UI -> resource 24171 -> Monitoring -> Schedules;
  
Actual results:
Collection interval for the metric 'Free Memory' has not been changed.

Expected results:
Collection interval for the metric 'Free Memory' is changed to 30 minutes.

Additional info:
Above works fine if interval method is not used and if the collection interval is set directly using milliseconds, for instance:

exec -f /home/JON_311/util.js
exec -f /home/JON_311/measurement_utils.js

mm = new MeasurementModule();

updates = { context: 'Resource', id: 24171, schedules: {'Free Memory': 1800000}};
mm.updateSchedules(updates);