ceph: Fix typo in the comment

Correctly spelled comments make it easier for the reader to understand
the code.

replace 'tagert' with 'target' in the comment &
replace 'vaild' with 'valid' in the comment &
replace 'carefull' with 'careful' in the comment &
replace 'trsaverse' with 'traverse' in the comment.

Signed-off-by: Yan Zhen <yanzhen@vivo.com>
Reviewed-by: Xiubo Li <xiubli@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>