Adjustments to configib to handle Rocky9 precreated connections

[dubmarm]

The PR is to fix an issue with configib that fails to configure an IB connection if it already exists

The modification include

files altered: xCAT/postscripts/configib

1. Take out a useless segment of arp_ignore and arp_filter that was clearing any sysctl.conf
2. Create a logic to perform nmcli con add if the $nic doesnt exist ELSE perform nmcli con modify
   • Otherwise an error is thrown stating a duplicate con exists with the same name and the adjustments dont occur

[CLAassistant]

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1 out of 2 committers have signed the CLA.

✅ dubmarm
❌ dmarm

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[Obihoernchen]

Thank you for this PR!
Can you please sign the CA?
Thank you!

[Obihoernchen]

@dubmarm could you please sign the CLA and revert the arp_ignore changes? Then I'll merge this.

[dubmarm]

I did sign the CLA, the webpage shows a little grey'ed out chckbox that says I signed it. Regarding reverting the arp_ignore I can do that.

[Obihoernchen]

Looks like you did use another mail for your commits. That's fine.
Yes, please revert the arp_ignore changes, then I can merge this PR.

[dubmarm]

1. I added my work email to my profile
2. I reverted the changes to line 391-394.

This should be good if you agree