Nits: clean the magic number for seek()

Change-Id: I65625ae7a41649e290636c95f0e694c065fe42dc
Signed-off-by: Shu Ming <shuming@linux.vnet.ibm.com>
Reviewed-on: http://gerrit.ovirt.org/11390
Reviewed-by: Dan Kenigsberg <danken@redhat.com>
Tested-by: Dan Kenigsberg <danken@redhat.com>