Fix #71542: disk_total_space does not work with relative paths

For ZTS builds, we need to expand the path given to `disk_free_space()`
and `disk_total_space()` to properly support the VC

Fix #71542: disk_total_space does not work with relative paths

For ZTS builds, we need to expand the path given to `disk_free_space()`
and `disk_total_space()` to properly support the VCWD.

Closes GH-7377.

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