syz-manager: don't create legacy corpus dir if it does not exist
syz-manager: don't create legacy corpus dir if it does not exist

hyz0906/syzkaller,hyz0906/syzkaller,zoulasc/syzkaller,hyz0906/syzkaller,zoulasc/syzkaller,google/syzkaller,google/syzkaller,xairy/syzkaller,dotweiba/syzkaller,google/syzkaller,google/syzkaller,zoulasc/syzkaller,dotweiba/syzkaller,dotweiba/syzkaller,xairy/syzkaller,hyz0906/syzkaller,hyz0906/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,zoulasc/syzkaller,google/syzkaller,xairy/syzkaller,xairy/syzkaller,xairy/syzkaller,google/syzkaller,dotweiba/syzkaller