Configuration read and write need to be symmetric

[davepuchyr]

If I query the configuration with iovnscli or the REST API I get *_period parameters in nanoseconds. When I try to update the configuration I have to specify periods as durations. That mismatch in time formats is a real pain since I have to specify all configuration parameters even if I just want to update one.

*_period flags for iovnscli should be in nanoseconds.