ceph-aio: make do_cmd return command output

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
ceph-aio: implement osd install

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
ceph-aio: delete various keyring when clean up

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
ceph-aio: remove all osds when perform clean command

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>
ceph-aio: move code for handling osd and mon to their place

Signed-off-by: Dunrong Huang <riegamaths@gmail.com>