Fix a long standing regression of readdir(3) in fdescfs(5) introduced in r1.48.  We were stopping at the first null pointer when multiple file descriptors were opened and one in the middle was closed.  This restores traditional behaviour of fdescfs.
Fix a long standing regression of readdir(3) in fdescfs(5) introduced
in r1.48.  We were stopping at the first null pointer when multiple file
descriptors were opened and one in the middle was closed.  This restores
traditional behaviour of fdescfs.

MFC after:	3 days

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