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What's changed and what's your intention?

fix #15978

If Doris FE and BE are on the same machine, the BE's address can be set to 127.0.0.1. However, RW might not be able to connect to it, so use the FE's host instead of the BE's host.
e.g.
In the e2e-doris-sink test, BE's origin address is 127.0.0.1:8040, after replace with FE host, it is doris-server:8040.

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