examples/dommigrate: Make retval portable
examples/dommigrate: Make retval portable

Currently, the dommigrate example returns 0 or 1 for success or
failure state, respectively. Except for a few cases where it
forgot to change the @ret variable just before jumping onto the
'cleanup' label. Making the code follow our usual pattern
(initialize @ret to an error value and set it to success value
only at the end) fixes those cases. Also, using EXIT_SUCCESS and
EXIT_FAILURE is more portable (even though on my system they are
just an alias to values the example already uses).

Signed-off-by: Michal Privoznik <83d82aaba2eed257f4814b0c239c260c4caaadf0@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Reviewed-by: Kristína Hanicová <e70d889c982bbe3b9ce2841af457ca911bff1baa@redhat.com>

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