core: cleanup - Fix typo in class name

Changed AttachDettachVmDiskParameters to AttachDetachVmDiskParameters.
Double-t in detach is misspelled.

Change-Id: I2b91c5754da60a5faca23b692baf3894b90962de
Signed-off-by: Vered Volansky <vvolansk@redhat.com>