Fix a bug in CIDR.contains(InetAddress) implementations

Related issue: #2767

Motivation:

CIDR.contains(InetAddress) implementations should always return true
when the CIDR's prefix length is 0.

Modifications:

- Make CIDR.contains(InetAddress) return true if the current cidrMask is
  0
- Add tests

Result:

Fixed the issue #2767