Description of problem:
vNIC profile will implicitly use the version of the DC to determine which custom device properties to display, however the DC level is not relevant and instead only the cluster level (which is determined by the VM using the profile).

When trying to set custom properties config key:
$ ~/devenv/ovirt-engine//bin/engine-config -s CustomDeviceProperties="{type=interface;prop={myProp=[a-zA-Z0-9-]+}}" --cver=3.2
Cannot set value {type=interface;prop={myProp=[a-zA-Z0-9-]+}} to key CustomDeviceProperties. Device custom properties are not supported in version 3.2



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


How reproducible:
Always


Steps to Reproduce:
1. Create a < 3.3 DC
2. Edit the management network profile
3.

Actual results:
The dialog always shows "No available keys"


Expected results:
It should be possible to set custom properties and use them in the profile


Additional info:
First of all the tying of DC version to the profile is, like in bug 1024209, unnecessary and limiting without good cause.

Secondly, I think device custom properties config value split by versions is just complicating the feature and I don't think it is a necessary complication, hence I suggest to consolidate the values into one and drop the version checks on the config value itself, that is not the way to do it anyway.
The version check should be on VM level (either when using the custom properties there, or running the VM).