pkg/bisect: detect when too many instances errored
pkg/bisect: detect when too many instances errored

We currently skip a commit iff all 10 instances errored.
But if, say, only 9 errored we consider it as OK,
but this significnalty reduces chances of detecting flaky crashes.
So skip if more than 2/3 errored.

Update #501

google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller