It appears that readdir() on Linux detects file types unreliably, always setting
the "d_type" field to DT_UNKNOWN for some less common filesystems. As a result,
all files were skipped and no certificate bundles were found when the state
directory was located on such filesystems.
Skipping "." and ".." instead of any non-regular files should be enough, as no
other non-regular files normally appear in this directory.
This closes#368 issue on GitHub.
b0a1266835