Parsing an AST for every java file wastes a lot of time when most
classes don't contain any DS annotations. Optimization: check if the
compilation unit contains a type annotated with @Component. If not, any
existing DS keys for this unit can be marked as abandoned and AST
parsing is not necessary.

Change-Id: Idd9588b543fda67f70e47efa4cb12657ca5a3253
Signed-off-by: Julian Honnen <julian.honnen@vector.com>