swtpm: Introduce --migration option and 'incoming' parameter

swtpm: Introduce --migration option and 'incoming' parameter

Introduce the --migration option along with the 'incoming' parameter
that allows to defer the locking of the storage until either

- the reception of the TPM's state is started
- a TPM command is about to be processed

Note that the reception of CMD_INIT does not enable the storage lock.

Signed-off-by: Stefan Berger <stefanb@linux.ibm.com>
Resolves: https://github.com/stefanberger/swtpm/issues/724