[BugFix] Fix error log to show the right agent type

[qianheng-aws]

Description

When agent runs failed, MLAgentExecutor always show the error log with Failed to run flow agent, no matter which type the current agent is.

# Before fix for a conversational agent:
[2024-08-07T11:07:01,763][ERROR][o.o.m.e.a.a.MLAgentExecutor] [c889f3b35c9d] Failed to run flow agent

# After fix:
[2024-08-07T11:11:08,935][ERROR][o.o.m.e.a.a.MLAgentExecutor] [c889f3b35c9d] Failed to run conversational agent

Related Issues

Check List

• [ ] New functionality includes testing.
• [ ] New functionality has been documented.
• [ ] API changes companion pull request created.
• [x] Commits are signed per the DCO using --signoff.
• [ ] Public documentation issue/PR created.

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