executor: treat fail-nth errors as non-fatal
executor: treat fail-nth errors as non-fatal

We see occasional ENOENT/EACCES errors returned.
It seems that fuzzer somehow gets its hands to it.

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