units: measure "factory-reset" into PCR 11 when we request factory reset

units: measure "factory-reset" into PCR 11 when we request factory reset

Let's make sure that the moment where factory reset is requested is
visible in the TPM PCR state, so that access to secrets is terminated.

This is particulary interesting when the system is booted with
systemd.unit=factory-reset.target on the kernel command line, requesting
a factory reset on the following boot. The preparations done in
userspace should already lose access to the TPM in that case.