NVMeoF and iSCSI fixes for IPv6

[mwilck]

Fixes for https://github.com/dracutdevs/dracut/pull/2184

Changes

I've only recently been able to make real tests with IPv6 and NVMeoF boot. This revealed the issues fixed in this PR.

The nvmf fixups should be squashed into timberlandmaster_final, the iSCSI patches should remain separate.

Checklist

• [x] I have tested it locally
• [x] I have reviewed and updated any documentation if relevant
• [ ] I am providing new code and test(s) for it

[mwilck]

@johnmeneghini, please merge into timberlandmaster_final to include this in the upstream PR.

[mwilck]

@aafeijoo-suse for information