Kohei Tokunaga

cri_keychain: preserve access to private registries across restart

1

### Issue Currently cri keychain holds registry creds only on memory. When stargz-snapshotter restarts, it doesn't have registry creds anymore so it starts to fail to access to the regisry....

Fix #1349 CRI plugins fails to perform GC because it fails to find root direcotry of stargz snapshotter. Recent containerd added `proxy_plugins.stargz.exports.root` field to config.toml for solving this issue so...

Following up https://github.com/containerd/stargz-snapshotter/pull/1892

Fix `select` didn't work with pipes and the timeout argument

3

This PR fixes an issue that the timeout argument for the select syscall wasn't applied to pipes and it returned immedeately instead of waiting for events. Although the select syscall...