Prevent intermittent race in attribute reader close #19537

There is a potential rare race possible whereby the c.running channel could be closed twice. Looking at the code I do not see a need for this c.running channel and therefore I think we can remove this. (I think the c.running might have been some attempt to prevent a hang but the use of os.Pipes should prevent that.) Signed-off-by: Andrew Thornton <[email protected]>

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