Set logbook/flowdetail/atomdetail meta to empty dict

Instead of setting to none, and then later setting to
a dictionary just by default set it to an empty dict
which makes it more clear what the intended usage of
the meta attribute is for.

Change-Id: Ic42c423d104f369a43227c4ef4563f1f99635fa0
Merge "Set logbook/flowdetail/atomdetail meta to empty dict"