[SSSD] [PATCH] Be extra careful when closing our nss sockets

[Simo Sorce]

This patch address bz670511/trac790

Makes sure there is less chance a broken application, on fork, closes
the socket under our feet and reuses the same fd for other purposes, and
then complains if we close with the socket.

Simo.

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Simo Sorce * Red Hat, Inc * New York