loop interval and time interval priority

[dyokelson]

Hi, while running a loop_monitor with the following command we found that if the time interval is not set, it will use a default setting and override the iteration interval.
For example, when measuring LULESH, running:
CALI_SERVICES_ENABLE=loop_monitor,memstat,trace,recorder CALI_LOOP_MONITOR_ITERATION_INTERVAL=20 ./lulesh2.0 -i 100 -s 45
results in somewhat unexpected behavior - where we actually get more frequent data than we want. A current workaround thanks to @daboehme is to set the CALI_LOOP_MONITOR_TIME_INTERVAL=0 which will turn it off and make the iteration interval the prioritized frequency. So running:
CALI_SERVICES_ENABLE=loop_monitor,memstat,trace,recorder CALI_LOOP_MONITOR_ITERATION_INTERVAL=20 CALI_LOOP_MONITOR_TIME_INTERVAL=0 ./lulesh2.0 -i 100 -s 45
has the expected behavior of producing data every 20 iterations.