common: remove log_early configuration option

common: remove log_early configuration option

After deciding to always enable tracking log in early phase, there's no
need to keep "log_early" option here and remove it directly.

Suggested-by: Kefu Chai <kefu@redhat.com>
Signed-off-by: Changcheng Liu <changcheng.liu@aliyun.com>
(cherry picked from commit dbdcb2535d0d463d92d90169175e0776a0ee58e3)

Conflicts:
	qa/tasks/ceph_manager.py [ already dropped in nautilus, commit
	  b8dd87424ecb ("qa/tasks/ceph_manager.py: don't use log-early
	  in raw_cluster_cmd") ]