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.
However, in the case of ModemRemoved there was a g_message. In fact this is infrequent, urfkill most of the times adds the modems as a result of a GetModems call, even when ofono starts after urfkill. So I think it is worthy to print this as can give us hints when something not usual happens, and it will print just a message per execution.