agent_install: Enable Agent upgrades

[bastelfreak]

The install.bash script from PE supports agent updates and upgrades since a long time. I don't see a reason why the task in peadm should abort if it isn't a new installation. I understand if the support team doesn't want to take responsibility for upgrades/updates, but I think we shouldn't block users/SDP consultants using it.

[timidri]

I also don't see a problem with this. @ody do you?

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[AaronShannon]

Hi @bastelfreak

Can you please rebase your branch with the latest from main? That way we can rekick the CLI checks since the previously run checks have now expired

[bastelfreak]

@AaronShannon done