Fix show.receiver statistics.
Fix show.receiver statistics.

Use current time for calculations,
not the start-time of celery.

Meisterschueler/ogn-python,glidernet/ogn-python,glidernet/ogn-python,Meisterschueler/ogn-python,kerel-fs/ogn-python,glidernet/ogn-python,glidernet/ogn-python,Meisterschueler/ogn-python,Meisterschueler/ogn-python