RDKEMW-10995: Fix to prevent double close issue

[ks734]

Description

Added proper fd validation and avoids closing the same fd twice

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Other (doesn't fit into the above categories - e.g. documentation updates)

Requires Bitbake Recipe changes?

• The base Bitbake recipe (meta-rdk-ext/recipes-containers/dobby/dobby.bb) must be modified to support the changes in this PR (beyond updating SRC_REV)

[Copilot]

Pull request overview

Fixes a file-descriptor lifecycle issue in the Logging plugin’s FileSink to prevent accidentally closing the same FD twice, especially when the output file falls back to /dev/null.

Changes:

• Treat fd 0 as valid by switching fd checks from > 0 to >= 0 in the /dev/null fallback path.
• Update destructor close logic to avoid double-closing when mOutputFileFd aliases mDevNullFd.
• Improve close error reporting by distinguishing “output file” vs “/dev/null” failures.

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