core: WAD in RemoveDiskSnapshotTaskHandler

Added a call to setWipeAfterDelete in
RemoveDiskSnapshotTaskHandler.buildRemoveSnapshotSingleDiskParameters.

Change-Id: Ib3f6896c4ad64ca5d3515b865dbab469d236100b
Bug-Url: https://bugzilla.redhat.com/1141702
Signed-off-by: Idan Shaby <ishaby@redhat.com>