Fix handling of nlookup in ientry
nlookup is only decremented on forget, and incremented on positive
fuse_reply_entry and fuse_reply_create responses.
By the way an ientry rozodiag command is added,
and forget is traced in rozofs fuse trace.
Merge branch 'hotfix/1.5.2' of https://github.com/rozofs/rozofs into hotfix/1.5.2