storage: scsi: invert logic in createVport
storage: scsi: invert logic in createVport

Check whether the alloc result is negative (which is
cannot happen with current code) to reduce churn in
the following commit.

Signed-off-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Reviewed-by: Peter Krempa <2cf5c04c61aa466e4a47bfedc747d17279c72ffc@redhat.com>

libvirt/libvirt,jfehlig/libvirt,zippy2/libvirt,jfehlig/libvirt,zippy2/libvirt,jfehlig/libvirt,nertpinx/libvirt,crobinso/libvirt,nertpinx/libvirt,zippy2/libvirt,jardasgit/libvirt,libvirt/libvirt,libvirt/libvirt,crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt,nertpinx/libvirt,libvirt/libvirt,jardasgit/libvirt,nertpinx/libvirt,olafhering/libvirt,crobinso/libvirt,jardasgit/libvirt,olafhering/libvirt,olafhering/libvirt,olafhering/libvirt,jardasgit/libvirt,crobinso/libvirt,jardasgit/libvirt,nertpinx/libvirt