core: remove unneeded set of parameters member

During ImportVm, the addStorageDomainMapping flag is set without need,
it's ignored during the execute phase of move or copy all image group
command when the parent command is import vm command and can cause to
unneeded deletion of source image mapping during the endWithFailure method.

Change-Id: I55bed0b63faef266cfc30fd8193238ee9dc1163d
Signed-off-by: Liron Aravot <laravot@redhat.com>