vfs_ceph_new: use 'ceph_new' for config-param prefix

vfs_ceph_new: use 'ceph_new' for config-param prefix

Use explicit 'ceph_new' prefix to each of the ceph specific config
parameters to avoid confusion with legacy 'vfs_ceph' module. Hence,
users will have in their smb.conf a format similar to:

...
[smbshare]
        vfs objects = ceph_new
        ceph_new: config_file = /etc/ceph/ceph.conf
        ceph_new: user_id = user1
        ceph_new: filesystem = fs1
        ...

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15686

Signed-off-by: Shachar Sharon <ssharon@redhat.com>
Reviewed-by: Anoop C S <anoopcs@samba.org>
Reviewed-by: Guenther Deschner <gd@samba.org>