When a thread fails to spawn, include the thread name in the error
message.

No longer init then deinit part of the engine at startup of the unix
socket mode.

Timeout checks would access certain fields w/o locking, which could lead
to thread safety issues.

Use a more precise calculation for timing out flows, using both the
seconds and the micro seconds.

The flow worker needs to get the opportunity to run the flow update
before globally making it's current timestamp available. This is to
avoid another thread using the time to evict the flow that is about to
get a legitimate update.

If seconds match a flow can still be timing out.

When timing out flows, use the timestamp from the "owning" thread. This
avoids problems with threads being out of sync with each other.

As this may mean that a threads ts is a bit ahead of the minimum time
the flow manager normally uses, it can evict flows a bit faster.

The idea of sealing the thread store is that its members can be accessed
w/o holding a lock to the whole store at runtime.

Some checks can be done w/o holding a lock:
- seeing if the flow matches the packet
- if the hash row needs a timeout check

This patch skips taking a lock in these conditions.