storage: Invert retval logic in virStorageBackendSCSITriggerRescan
storage: Invert retval logic in virStorageBackendSCSITriggerRescan

Rather than initialize to 0 and change to -1 on error, let's do the
normal operation of initializing to -1 and set to 0 on success.

Signed-off-by: John Ferlan <87558058f6f829e5ec976c8ef960720af4ff9c7d@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

andreabolognani/libvirt,libvirt/libvirt,eskultety/libvirt,crobinso/libvirt,libvirt/libvirt,nertpinx/libvirt,nertpinx/libvirt,crobinso/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,nertpinx/libvirt,crobinso/libvirt,jardasgit/libvirt,eskultety/libvirt,olafhering/libvirt,zippy2/libvirt,jardasgit/libvirt,jfehlig/libvirt,crobinso/libvirt,eskultety/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,eskultety/libvirt,jfehlig/libvirt,eskultety/libvirt,zippy2/libvirt,jfehlig/libvirt,nertpinx/libvirt,olafhering/libvirt,olafhering/libvirt,zippy2/libvirt,libvirt/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,jardasgit/libvirt,jardasgit/libvirt,jardasgit/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,olafhering/libvirt,nertpinx/libvirt,fabianfreyer/libvirt,fabianfreyer/libvirt,zippy2/libvirt,libvirt/libvirt