Bugfix 1339

[rajnikantsolarwinds]

No description provided.

[grossmj]

This PR is incomplete to solve #1339

For instance editing a Qemu template gives this error:

I cannot configure a MAC address for custom adapters:

For info here is what we have in the server to validate a custom adapter:

    adapter_number: int
    port_name: str
    adapter_type: Optional[str] = None
    mac_address: Optional[str] = Field(None, regex="^([0-9a-fA-F]{2}[:]){5}([0-9a-fA-F]{2})$")

adapter_number and port_name are mandatory. adapter_type and mac_address are optional.