vfs_ceph: Implement SMB_VFS_FGET_DOS_ATTRIBUTES to preserve create_time

vfs_ceph: Implement SMB_VFS_FGET_DOS_ATTRIBUTES to preserve create_time

In order to avoid the dependency on dos attribute for create_time we now
preserve the btime before parsing dos attribute which may update btime
from its value with an old one unless we explicitly reset dos attribute
with new create_time in SMB_VFS_FNTIMES implementation. Therefore have
an implementation for SMB_VFS_FGET_DOS_ATTRIBUTES to save and restore
updated create_time.

Signed-off-by: Anoop C S <anoopcs@samba.org>
Reviewed-by: Ralph Boehme <slow@samba.org>