rst: Error code got hidden by successful core read
rst: Error code got hidden by successful core read

The ret is overwritten by core read sub-routine. Need
to reset it to -1 to keep failing in case of e.g. last
pid sysctl write.

Reported-by: Neal Becker <d96e5fd9cb509d18620b7c3441686124f50f1aea@gmail.com>
Signed-off-by: Pavel Emelyanov <c9a32589e048e044184536f7ac71ef92fe82df3e@parallels.com>

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