rgw_file: "exact match" invalid for directories, in RGWLibFS::stat_leaf()
rgw_file: invalid use of RGWFileHandle::FLAG_EXACT_MATCH
The change which introduced this flag also caused it to be
given as the flags argument to RGWLibFS::stat_leaf() when called
This was incorrect: in particular, when a directory is known only
as a common prefix of other objects, the AWS namespace mapping
convention requires lookup("foo") to match a non-materialized
instance of "foo/" (case 2 in RGWLibFS::stat_leaf's stat loop).