Use NTP throughout

[aaaaalbert]

NorNet node byaasen.ntnu.nornet has a positive clock offset of almost three days. This is also reflected in the nodemanager log timestamps, e.g.

1438289707.58:PID-17774:myname = 25ab519d15fc115c5c172424b3cd8cdbc7660414:1224

when the Unix time (on my machine) really is 1438061487.

The nmAPI commands and signatures use NTP time as long as this is available. I think the main nodemanager process should too.