Add automatic fallback to TPM emulation on devices that do not have a TPM device

[Martin-Weiss]

Describe the solution you'd like:
We want to use a single registration endpoint for all our devices. Some have TPM and some others do not have TPM or even have fTPM.

At the moment we have to enable or disable TPM on the endpoint - so one setting rules them all and we would have to use two different endpoints one for devices with and one for the ones without TPM..

It would be great if elemental-register could automatically fall back to tpm emulation if a device does not have a TPM..

Anything else you would like to add:
Maybe we need an additional parmeter for fallback_to_tpm_emulation=true/false

[kkaempf]

TPM is a security measure, esp. ensuring that the right machines connect to the cluster.

A fallback should be explicit, like emulate-tpm: fallback or similar.