Avoid double call to set ofono's online property

On initialization a double call to set-soft was being done for the ofono device. This caused bugs LP #1392397 and #1379807.
What I'm saying, is please leave these messages g_debug. There are other messages from the arbitrator, from devices, etc. which should already be notifying that there is an added device (and if not, that would be a better place than only logging it for modems). The goal is to not have more normal syslog messages than necessary. We can always enable debugging when and if it is needed.