pie: Print timestamps in restorer

Nowadays we have parasite and restorer logs just start with pie:
prefix. Let's add timestamps in restorer too.

For parasite adding timestamps would require passing the start
timeval through the libcompel which is not (yet) clear how to do.

travis-ci: success for pie: Print timestamps in restorer
Signed-off-by: Pavel Emelyanov <xemul@virtuozzo.com>