gluster: Handle changed glfs_ftruncate signature

gluster: Handle changed glfs_ftruncate signature

New versions of Glusters libgfapi.so have an updated glfs_ftruncate()
function that returns additional 'struct stat' structures to enable
advanced caching of attributes. This is useful for file servers, not so
much for QEMU. Nevertheless, the API has changed and needs to be
adopted.

Signed-off-by: Prasanna Kumar Kalever <prasanna.kalever@redhat.com>
Signed-off-by: Niels de Vos <ndevos@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
(cherry picked from commit e014dbe74e0484188164c61ff6843f8a04a8cb9d)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>