Lps 40068 Improve usage of org.apache.velocity.VelocityContext

Hi Shuyang, 

According to profile, I found we are doing needless wrap on VelocityContext, please see the description of this ticket:

VelocityContext is chainable, means it has both a local map and a inner context referring to another VelocityContext, every time you do get/contains, you need to search local map and all the inner contexts one by one before you find a result, good part is the inner contexts can keep untouched when you do put.
In our scenario, we are doing deep copy to create a VelocityContext, so we do not need a inner context to avoid being modified.


Thanks.
Tina.