Recalculate network estimate after work is completed.

Don't recalculate the network byte numbers when a JobWorkItem has been
dequeued since the work still needs to be done. Instead, wait until the
work has been marked completed to recalculate the network byte numbers.

Bug: 255828754
Test: N/A
Change-Id: I0deb5d35293a8780329696d2c467270e59d32e05