fix: remove Docker container lifecycle management (dead code since 2016)

[viniciusferrao]

Summary

Remove Docker container lifecycle management (mgt=docker, mkdocker, rmdocker, lsdocker) from xCAT.

This was added in 2015-2016 as an experiment targeting Docker API v1.22 on Ubuntu only. Documentation and man pages were deliberately removed in 2019 (PRs xcat2#6222 and xcat2#6324) with the original developer's approval. The plugin has had no functional code changes since April 2016, was never listed as a valid mgt value in Schema.pm, and no user has ever filed an issue about it.

Changes

• Delete xCAT-server/lib/xcat/plugins/docker.pm (1,142 lines)
• Delete xCAT/postscripts/setupdockerhost
• Delete xCAT-server/share/xcat/scripts/setup-dockerhost-cert.sh
• Delete Docker test cases and bundle entries
• Remove Docker attribute definitions from Schema.pm
• Remove Docker host cert generation from xcatconfig
• Remove client symlinks (mkdocker, rmdocker, lsdocker) from RPM spec and debian links
• Remove Docker usage entries from Usage.pm and AAAusage.pm
• Remove Docker credential handling from credentials.pm
• Remove Docker regression path from xCATreg
• Clean Docker attributes from man7 generated docs

The "Running xCAT in Docker" documentation (dockerized_xcat/) is retained — it documents containerizing xCAT itself, not the removed mgt=docker feature.

Test plan

• perl -c perl-xCAT/xCAT/Schema.pm passes
• Zero remaining references to mkdocker/rmdocker/lsdocker/setupdockerhost/xcatdockerca/mgt=docker
• No sensitive strings in diff
• Adversarial review converged (4 passes)

Closes xcat2#7518

[viniciusferrao]

Live Validation on cloyster (RHEL 8, xCAT 2.17.0)

Verified on the lab management node that removing Docker lifecycle code has no impact on existing functionality.

Environment

• xCAT 2.17.0 on RHEL 8 (x86_64)
• POWER9 AC922 managed via OpenBMC

Results

No Docker nodes exist in the cluster:

# tabdump vm
#node,mgr,host,... (empty - header only)

# lsdef -t node -w mgt==docker
No object definitions have been found

Docker attributes are already guarded — cannot be set without mgt=docker:

# chdef -t node power9bmc dockerhost=test
Error: Cannot set the attr='dockerhost' attribute unless mgt value is docker.

VM/BMC commands unaffected:

# rpower power9bmc stat
power9bmc: on

# rinv power9bmc firm
power9bmc: BMC Firmware Product: op940.90-4-0-gbebb0d890a (Active)*
power9bmc: HOST Firmware Product: IBM-witherspoon-ibm-OP9-v2.4.1-4.67-prod (Active)*

# lsdef power9bmc -i mgt,bmc,groups
Object name: power9bmc
    bmc=10.20.0.56
    groups=all
    mgt=openbmc

Existing Docker artifacts on 2.17.0 (to be removed on upgrade):

# ls /opt/xcat/lib/perl/xCAT_plugin/docker.pm     # exists (1142 lines, unused)
# ls /opt/xcat/share/xcat/scripts/setup-dockerhost-cert.sh  # exists (unused)
# ls /etc/xcatdockerca/cert/                        # exists (generated by xcatconfig, never used)

Patched xcatconfig diff confirmed: Docker cert generation block cleanly removed, adjacent setup-server-cert.sh logic untouched.

Conclusion

Zero Docker-managed nodes in production. Schema guard (only_if => 'mgt=docker') means removal of aliases is invisible to all existing node definitions. VM table is empty. All BMC/power/inventory commands work normally.