MB-19048 Do not grab fhandle_idx_lock in filemgr_free_func()
MB-19048 Do not grab fhandle_idx_lock in filemgr_free_func()

- The file already became unreachable so that grabbing lock is
unnecessary.

Change-Id: If6a6dff8511c6c76ac64bbb0cf94feba9bf78831
Reviewed-on: http://review.couchbase.org/62764
Reviewed-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>
Tested-by: Chiyoung Seo <fcffc23db27b19ee4ebba46695ee6b50e09216a2@couchbase.com>

hisundar/forestdb,wurikiji/forestdb,hisundar/forestdb,couchbase/forestdb,wurikiji/forestdb,couchbase/forestdb