[CDM perm sync] Remove SystemDataTransferRequest when disassociate

Fix: 220921569

Remove all the system data transfer requests for the association when
it's being disassociated.

Fix: 220921569

Test: Manually tested it in the CDM test app. Added unit tests.
Change-Id: I24fd4fd5639e0801e4f5df6b5616c3910b87f247