remove bogus code: each sliver can remember at most one async read request.  Should this happen, we would be in great trouble.  iozone -a, self build, kernel builds on DIO path.
remove bogus code: each sliver can remember at most one async read request.  Should this happen, we would
be in great trouble.  iozone -a, self build, kernel builds on DIO path.


git-svn-id: ae92b08b608af1c8cefa3e10d2325ea527204e07@24774 3eda493b-6a19-0410-b2e0-ec8ea4dd8fda

pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable,pscedu/slash2-stable