osds: use ceph osd stat instead of ceph status

osds: use ceph osd stat instead of ceph status

Improve the checked way of the OSD created checking process.
This replaces the ceph status command by the ceph osd stat command.
The osdmap structure isn't needed anymore.

$ ceph status -f json | wc -c
2001
$ ceph osd stat -f json | wc -c
132
$ time ceph status -f json > /dev/null

real    0m0.563s
user    0m0.526s
sys     0m0.036s
$ time ceph osd stat -f json > /dev/null

real	0m0.457s
user	0m0.411s
sys	0m0.045s

Signed-off-by: wangxiaotong <wangxiaotong@fiberhome.com>