security/sshguard: Upgrade to 2.4.2

Major changes:

• Recognize rejections from Postfix's postscreen daemon
• The parser can now be changed using the PARSER and POST_PARSER options
• Remove some false positive attack signatures for SSH and Cyrus
• Adjust log verbosity of some log messages
• The firewalld backend now uses firewall-cmd instead of iptables to flush block lists

Full changelog : https://bitbucket.org/sshguard/sshguard/src/v2.4.2/CHANGELOG.rst

PR: 256575
Reported by: <sirdice@gmail.com>
Approved by: Kevin Zheng <kevinz5000@gmail.com> (maintainer)