fix #3134 vSphere UI host create/edit requires some fixes

[mmatuska]

fix issue #3134

Host create/edit mode:

• Editing of existing VMs is not yet supported, networks and storage should by grayed out by now
• The new network interface type selection does not detect already configured values
• The thick/thin provisioning checkbox should not always be on
• If cloning a VM, the Virtual Machine options should be identical as source VM and editable (not grayed out)

[domcleal]

Minor thing, but perhaps cache networks outside of the loop? I think we've learned that vSphere queries are expensive :)

[domcleal]

Thanks for the contribution @mmatuska. Merged as 29769a4 for Foreman 1.4.0. Cheers!