Avoid repeated logging of the file name when ReadConfig returns an
error.

https://r.android.com/2963904 made ReadConfig include the file name in
the error if the file cannot be read, but some call sites added it as
well. Make it consistently the responsibility of ReadConfig.

Also shorten an error message where the path itself is good enough to
identify the call site.

Test: presubmits
Bug: 325107109
Change-Id: I0c7d6c0ea3a7fb5d2ba1fa6aa25557080ac4d630
1 file changed