Further clean up init scripts

There is some additional cleanup/improvements to be done for the init scripts. In particular, the file ownership of the keytabs is something I want to revisit. The other thing is the installation of ceph-common, which should only happen if the scheduler backend is Ceph (this can save quite a bit of startup time in a development setup where VFS is used).

Additionally, perhaps some of the readiness probes can be done better (making things more robust and responsive to failure).