OPTIM: task: readjust CPU bandwidth distribution since last update

OPTIM: task: readjust CPU bandwidth distribution since last update

Now that we can more accurately watch which connection is really
being woken up from itself, it was desirable to re-adjust the CPU BW
thresholds based on measurements. New tests with 60000 concurrent
connections were run at 100 Gbps with unbounded queues and showed
the following distribution:

     scenario           TC0 TC1 TC2   observation
    -------------------+---+---+----+---------------------------
     TCP conn rate     : 32, 51, 17
     HTTP conn rate    : 34, 41, 25
     TCP byte rate     :  2,  3, 95   (2 MB objets)
     splicing byte rate: 11,  6, 83   (2 MB objets)
     H2 10k object     : 44, 23, 33   client-limited
     mixed traffic     : 18, 10, 72   2*1m+1*0: 11kcps, 36 Gbps

The H2 experienced a huge change since it uses a persistent connection
that was accidently flagged in the previous test. The splicing test
exhibits a higher need for short tasklets, so does the mixed traffic
test. Given that latency mainly matters for conn rate and H2 here,
the ratios were readjusted as 33% for TC0, 50% for TC1 and 17% for
TC2, keeping in mind that whatever is not consumed by one class is
automatically shared in equal propertions by the next one(s). This
setting immediately provided a nice improvement as with the default
settings (maxpollevents=200, runqueue-depth=200), the same ratios as
above are still reported, while the time to request "show activity"
on the CLI dropped to 30-50ms. The average loop time is around 5.7ms
on the mixed traffic.

In addition, one extra stress test at 90.5 Gbps with 5100 conn/s shows
70-100ms CLI request time, with an average loop time of 17 ms.