Bhv 10114 Break down updateMetric() to increase performance

After model added or removed, you should update index bound.
Currently updating index bound logic is included in updateMetric(), so if you want to update index bound then you will undergo redundant work load. 
To increase performance, I pull update index bound logic out of updateMetric()

Enyo-DCO-1.1-Signed-off-by: David Um david.um@lge.com
Hi @DavidUM, should we move this conditional check into the `updateIndexBound` function? This could protect us if we were to ever call `updateIndexBound` directly at create time and we may not have a collection defined yet. Let me know what you think, thanks!