ceph-disk-prepare: handle any combination of file/partition/blkdev for data/journal

Signed-off-by: Sage Weil <sage@inktank.com>
ceph-disk-activate: remove in-the-way symlinks in /var/lib/ceph/osd

Signed-off-by: Sage Weil <sage@inktank.com>
ceph-disk-activate: be marginally more helpful

Either --dir or --mount is required.

Signed-off-by: Sage Weil <sage@inktank.com>
ceph-disk-activate: detect whether PATH is mount or dir

This is simpler.  Just detect what the path is and Do The Right Thing.

Closes #3341 (which wanted to make --mount the default)

Signed-off-by: Sage Weil <sage@inktank.com>
ceph-disk-activate: fix stray symlink removal

Signed-off-by: Sage Weil <sage@inktank.com>