Removed unused methods from db.api

Since 406ff304bb09f144a59448e0e9d2d01160c7d553 reservation methods
is not called directly so it can be removed from the public API

Related to blueprint db-cleanup

Change-Id: I5a62d0528705b6773f8667375b4e8e3922a1bd15
Merge "Removed unused methods from db.api"