tests: fix, typo schedutils/cpuset

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>
tests: split off losetup scsi_debug part

It's a pity that we would skip the whole test if scsi_debug is not
available.

Signed-off-by: Ruediger Meier <ruediger.meier@ga-group.nl>