Implement functions for managing the storage of the external swtpm as well
as starting and stopping it. Also implement functions to use swtpm_setup,
which simulates the manufacturing of a TPM, which includes creation of
certificates for the device.

Further, the external TPM needs storage on the host that we need to set
up before it can be run. We can clean up the host once the domain is
undefined.

This patch also implements a small layer for external device support that
calls into the TPM device layer if a domain has an attached TPM. This is
the layer we will wire up later on.
Signed-off-by: NStefan Berger <stefanb@linux.vnet.ibm.com>
Reviewed-by: NJohn Ferlan <jferlan@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>