Remove method getNumberOfPatchSets() from Change.

Removed the only use of the method. Fixed RebaseChange to pass in
the db object.

Some other minor cleanups are included too.

This is part of the code cleanup to remove the nbrPatchSets field.

Change-Id: Iaa7431ea9c96e19c008d8ec25d774e0f7240ba35
4 files changed