Description of problem:
When building edge-installer image, user cannot set hostname in the create wizard, this is correct because edge-installer does not support it. But, if the blueprint already has a hostname, for example, customer set the hostname when building other images, and now they will always fail with try to build edge-installer image, and there is no error message to indicate what's going wrong.

The only thing they can do, is to create other types of image, and remove the hostname, save the blueprint, and then go back to create edge-installer again.

We better fix it, but in one hand we should not allow customer to set/edit/remove hostname in create wizard, and in the other hand, customer also cannot remove it if the blueprint already have the hostname.

Version-Release number of selected component (if applicable):

How reproducible:
100%

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