`select into` may fail if `HADOOP_CONF_DIR` or `YARN_CONF_DIR` env are accidentally configured

**Bug Description**
`select into outfile '/tmp/out.csv'` may fail if the `HADOOP_CONF_DIR` or `YARN_CONF_DIR` environmental variables are accidentally configured and its `defaultfs` is `hdfs`.

**Expected Behavior**
For `outfile '/tmp/out.csv'`, users expect to write into local filesystems.
Possible solutions may be:
- add Q&A to show the potential issue
- guide users to specify 'file:///tmp/out.csv' to avoid the confusion

**Steps to Reproduce**

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