Set default timeout for the flow manager to wake up to 1 second. The 0.4 sec
performed best on a Xeon, but in kvm vm's it was horrible:
32 bit vm: 60% cpu for flowmgr when idle.
64 bit vm: 30% cpu for flowmgr when idle.
With the 1 second timeout both are at 0.3% cpu.
Short sleep can lead to some really annoying performance issue in
some environnement like virtual systems. This technic was used in
the flow manager. This patch uses an alternate approach based on
a timed condition which is triggered each time a new flow has to
be created. This avoid to run out of flow. A counter is also done
to be able not to run the cleaning code at each new flow.