kernel: sched: LOAD_FREQ (4*HZ+61) avoids loadavg Moire [AndreiLux]

LOAD_FREQ is (5*HZ+1) to avoid high load average when idle: http://kerneltrap.org/mailarchive/linux-kernel/2007/10/3/328568

I suggest (4*HZ+61) for a better distribution.

With some seconds based load (like SSL heartbeats) and LOAD_FREQ at (5*HZ+1) I see Moire patterns like inverse sawtooth, since 2 or 3 probes hit the jobs (load increases quickly), followed by several probes missing it.

A 4.61 sec interval gives optimal distribution over when within a second a probe is taken, as .61 is close to golden ratio phi 1.618... (test in http://ripke.com/goldenratio.c).

12*4.61 = 55.32 secs is still close to a minute, and 13*4.61=59.93 is even closer than the current 12*5.01=60.12 (with exponents EXP_x adjusted to a ratio of 13 instead of 12).