Use the common utility function, which contains checks on return values
and first calls F_GETFD as recommended by POSIX.1-2001, instead of
manually calling fcntl.

CID: 1374831
Signed-off-by: NStefano Stabellini <sstabellini@kernel.org>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NGreg Kurz <groug@kaod.org>
CC: anthony.perard@citrix.com
CC: groug@kaod.org
CC: aneesh.kumar@linux.vnet.ibm.com
CC: Eric Blake <eblake@redhat.com>