Revert "Makefile: fix ceph_sbindir"

This reverts commit 352f362567bf270d0896fb7573df4ae5139a56fb.

Reverting this commit because it causes problems with the debian build, and
reopening #5492.   The root problem appears to be lack of support by GNU
autotools for installing into both /sbin and /usr/sbin using the standard
location variables.

Signed-off-by: Gary Lowell  <gary.lowell@inktank.com>