Bugfix for HDF5 plugin; readded collective_md.

src/ior.h

@@ -179,6 +179,8 @@ typedef struct
     char*       URI;                 /* "path" to target object */
     size_t      part_number;         /* multi-part upload increment (PER-RANK!) */
     char*       UploadId; /* key for multi-part-uploads */
+    int         collective_md;       /* use collective metatata optimization */
+ 
 
     /* RADOS variables */
     rados_t rados_cluster;           /* RADOS cluster handle */