Wait time is negative when a finished VM is re-submitted to the broker

[manoelcampos]

When a finished VM is re-submitted to start executing again, its arrival time is updated by the broker to the current simulation time, but the creation time is not. It remains the value from the previous submission.
This way, the creation time is smaller than the arrived time for VM resubmissions, causing a negative wait time.

If we just reset creation time to -1, we lose the information about the previous creation time.
The wait time should represent the total time the VM has waited during all the times it was re-submitted to the broker.
Before resetting the creation time, we have to add up the previous wait time to a new totalWaitTime attribute, then reset the creation time. The creationTime and previous waitTime attributes will represent the last time VM was created and last wait time, respectively.

Related Issues

• CustomerEntityAbstract.getWaitTime returns negative value when the entity was not created yet. #350
• PowerModelHostSimple is not considering the total power consumption when a Host powers on and off multiple times #327 : this is a similar issue where the Host startup/shutdown power consumption was added up every time the host switches on/off. The same needs to be done for the wait time.