discuss whether need to consider prewarmedPool as consumed memory resources

[甯尤刚]

Hi, guys
​
    I wrote a pr here: https://github.com/apache/openwhisk/pull/4870
    this pr's target: make prewarmedPool as `already consumed memory 
resources`, this pr has an benefit that if consider prewarmedPool as consumed 
memory resource, can aovid to do  much `cold start a container` when the time 
of `space is consumed finished` is coming
​
    Have any suggestion?