BootMessage: Only display package name during optimization.

The previous implementation caused the package name to show up for
other messages such as "Starting apps." or "Finishing boot.". Now
we check if the base message starts with "Optimizing" and only
display the package name if that is true.

Change-Id: I2a9c9df8ce06c5016557e2f227c7f308f688ce8a
Merge "BootMessage: Only display package name during optimization." into kitkat