linuxrbd: remove obsolete comment on close()

Commit 1d51eb64ac changed close() to no
longer be a noop, rendering the comment to explain its reasoning
irrelevant.

Change-Id: Ic10a8697300e6ba4db20d8b40c86a69446db9acb

os_brick/initiator/linuxrbd.py

@@ -227,9 +227,5 @@ class RBDVolumeIOWrapper(io.RawIOBase):
         """
         raise IOError(_("fileno() not supported by RBD()"))
 
-    # NOTE(dosaboy): if IO object is not closed explicitly, Python auto closes
-    # it which, if this is not overridden, calls flush() prior to close which
-    # in this case is unwanted since the rbd image may have been closed prior
-    # to the autoclean - currently triggering a segfault in librbd.
     def close(self):
         self.rbd_image.close()