warn/error count limit for check-task/start-task has wrong granularity

[lance6716]

What did you do?

Sometime a checking item level is "warn", but internal errors list level is "fail"

in below case, when we only limit to output 1 error (foe example, by check-task ... --error 1), DM will only output suberror a. But it's better to output check item B

- check item A, warn
   - suberror a, fail
   - suberror b, fail
- check item B, fail 

What did you expect to see?

No response

What did you see instead?

No response

Versions of the cluster

DM version (run dmctl -V or dm-worker -V or dm-master -V):

(paste DM version here, and you must ensure versions of dmctl, DM-worker and DM-master are same)

Upstream MySQL/MariaDB server version:

(paste upstream MySQL/MariaDB server version here)

Downstream TiDB cluster version (execute SELECT tidb_version(); in a MySQL client):

(paste TiDB cluster version here)

How did you deploy DM: tiup or manually?

(leave TiUP or manually here)

Other interesting information (system version, hardware config, etc):

>
>

current status of DM cluster (execute query-status <task-name> in dmctl)

(paste current status of DM cluster here)

[lance6716]

introduced by pingcap/dm#1624