1) Removed some remaining unsupported ceph-disk related code.
2) Refactored the code that determines when a disk should be
zapped. Now there will be only one place where disk_zap is
called.
3) Refactored the code that determines when LVM prepare should
be called.
4) Improved the logging within the OSD init files
Change-Id: I194c82985f1f71b30d172f9e41438fa814500601