core: cleanup in CommandBase

1. Move field declarations up to the beginning of the class
2. Change the style of comments on fields to more compact style
3. Rename isReleaseExecute field to releaseLocksAtEndOfExecute to
conform the java standard and be more expressive

Change-Id: I551e00b86f18b62f95828b14f5fe54280eea6bb0
Signed-off-by: Arik Hadas <ahadas@redhat.com>