Fix coverage CI job (#42322)

It has been failing for a few days:

```
lcov: ERROR: lcov: ERROR: (inconsistent) mismatched end line for test_path_exists_body at /home/runner/work/systemd/systemd/src/test/test-path.c:158: 158 -> 185 while capturing from build/mkosi.builddir/arch~rolling~x86-64/test-path.p/src_test_test-path.c.gcno
	(use "lcov --ignore-errors inconsistent ..." to bypass this error)
```