This is required as the PKCS#11 library needs to be reinitialized after
forking. This was causing a problem with ipropd.
This fix appears to incur a repeatable 10ms performance penalty on aes-test.
Caching the initialization status using a once control and invalidating it
on fork provided no measurable performance benefit on Solaris 11. Other
approaches would not be thread-safe or would involve more intrusive code
changes, such as exposing heimbase's atomics.
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