V3: Check log directory

[Martin-Zeithaml]

Please check if your PR fulfills the following requirements. This is simply a reminder of what we are going to look for before merging your PR. If you don't know all of this information when you create this PR, don't worry. You can edit this template as you're working on it.

• DCO signoffs have been added to all commits, including this PR

PR type

What type of changes does your PR introduce to Zowe? Put an x in the box that applies to this PR. If you're unsure about any of them, don't hesitate to ask.

• Bugfix

Relevant issues

Partially fixes #4062

Changes proposed in this PR

• When --log-dir used for zwe command is a file, the command might end in the series of errors.

Does this PR introduce a breaking change?

• No

Test

/zowe: head ./manifest.json | grep version
  "version": "3.1.0",
/zowe: cd bin/
/zowe/bin: ./zwe start -c ./zwe -l ./zwe
Error ZWEL0102E: Invalid parameter --log-dir=./zwe (not a directory)

[github-actions]

build 6363 SUCCEEDED.
Link to workflow run: https://github.com/zowe/zowe-install-packaging/actions/runs/11609639040

[github-actions]

Test workflow 5641 is started.
Running install test: Convenience Pax
The zowe artifact being used by this test workflow: libs-snapshot-local/org/zowe/3.1.0-PR-4064/zowe-3.1.0-pr-4064-6363-20241031095312.pax
Running on machine: zzow10
Result: FAILURE
Link to workflow run: https://github.com/zowe/zowe-install-packaging/actions/runs/11609726216