Refactor snapshot code

Snapshot manipulation code and logic is now spread across multiple classes
and is becoming difficult to maintain and understand. This is an attempt to
simplify the implementation and make it easy to move forward.

Change-Id: I34e61c9d4bb4663d5f87d6c11fb6ed75c1bb33f2
Signed-off-by: Moiz Raja <moraja@cisco.com>