manager: save more trailing output
manager: save more trailing output

In some crash logs I see trimmed oops messages,
because fuzzer outputs executing programs.

google/syzkaller,sploving/syzkaller,hyz0906/syzkaller,zoulasc/syzkaller,hyz0906/syzkaller,sploving/syzkaller,hyz0906/syzkaller,zoulasc/syzkaller,dotweiba/syzkaller,sploving/syzkaller,sploving/syzkaller,zoulasc/syzkaller,xairy/syzkaller,xairy/syzkaller,dotweiba/syzkaller,xairy/syzkaller,zoulasc/syzkaller,xairy/syzkaller,xairy/syzkaller,lorenzo-stoakes/syzkaller,dotweiba/syzkaller,hyz0906/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,google/syzkaller,lorenzo-stoakes/syzkaller,xairy/syzkaller,lorenzo-stoakes/syzkaller,google/syzkaller,hyz0906/syzkaller,dotweiba/syzkaller,xairy/syzkaller