volume: fix validateCreateVolumeParams exception

The validateCreateVolumeParams check was returning an inconsistent
exception: IncorrectFormat with the parent volume uuid as argument.
The IncorrectFormat exception should return a format and not a
volume uuid.

Change-Id: I874cfbad8091396548463b98a13249a25baf9e9f
Signed-off-by: Federico Simoncelli <fsimonce@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/28226
Reviewed-by: Nir Soffer <nsoffer@redhat.com>
Reviewed-by: Dan Kenigsberg <danken@redhat.com>