- Closes#1520.
- Using URL for filesystem paths is bad practice. FilePath is safer and
more ergonomic.
- Same pattern as #1480 (HostDNSResolver) and #1518 (PacketFilter).
- Current DirectoryWatcher fails if `/etc/resolver` does not exist. This
PR fixes DirectoryWatcher to handle non-existing `/etc/resolver`
directory. If that directory does not exist, it first watches `/etc`
directory to check if `/etc/resolver` directory is created later. Once
it detects new `/etc/resolver` directory, it starts watching new DNS
resolver files there.
- This PR also fixes to log the exception thrown by API server's tasks.
- Closes#1207