Instruct readers to use "mkdir /mnt/cephfs1" to create a mountpoint
before using "ceph-fuse" to mount a filesystem, if "/mnt/cephfs1"
doesn't already exist. cf.
https://github.com/ceph/ceph/pull/56831#discussion_r1561102227
Signed-off-by: Zac Dover <zac.dover@proton.me>