FDB appends duplicate DB headers with no user data breaking GSI compact_upto

GSI tracks all fdb_commit()s and their corresponding snapshot markers.
So if during full compaction commit forestdb appends a DB header which carries no additional user data (gatherStaleRegions) from the previous commit, then it breaks GSI compact_upto() because the new snapshot marker and previous marker are identical from application perspective.
The fix is to adapt forestdb to never append a DB commit header when there is no delta data from application.