Fix a case where one inaccessible plugin search path stops the whole
search and prevents latter paths from being scanned.
Remove a preliminary `Stat` call that verifies whether path is an actual
directory and is accessible.
It's unneeded and doesn't actually check whether the directory can be
listed or not.
`os.ReadDir` will fail in such case anyway, so just attempt to do that
and ignore any encountered error, instead of erroring out the whole
plugin candidate listing.
Signed-off-by: Paweł Gronowski <pawel.gronowski@docker.com>
6de3d71ab6