locks were not aquired because the user buffers were not wired, thus it was
possible that that SYSCTL_OUT could sleep, causing a number of different
problems such as lock ordering issues and dead locks.
-Wire user supplied buffer to ensure SYSCTL_OUT will not sleep.
-Pickup ifnet locks to protect the list.
-Where applicable pickup address locks.
-Pickup radix node head locks.
-Remove splnet stubs
-Remove various comments about locking here, because they are no
longer needed.
It is the hope that these changes will make sysctl_rtsock MP safe.
MFC after: 3 weeks
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