swtpm: wait for pidfile

swtpm: wait for pidfile

swtpm may take a little bit to daemonize, so the pidfile might not be
available right after run_command. Causes an ugly warning about using an
undefined value in a match, so wait up to 5s for it to appear.

Note that in testing this loop only ever got to the first or second
iteration, so I believe the timeout duration should be more than enough.

Also add a missing 'usleep' import, 'usleep' was used before but never
imported, apparently the other case never got triggered...

Signed-off-by: Stefan Reiter <s.reiter@proxmox.com>