t4: two fixes for instance-ware loadavg

1. instance's runq in /proc/loadavg is still global, change it to instance's internal number.
2. Do not reset global counter 'avenrun'. Here it's intent to initialize cpuacct's avenrun,
but no need since we already use kzalloc. The bug has effect on global loadavg while
new cpuacct cgroup is created.


Signed-off-by: Sha Zhengju <handai.szj@taobao.com>