nway_conference == true was evaluating as true regardless if nway_conference was set to true or false, just as long as it had a value of any kind.
This also fixes it so that you can set nway_conference to false in the default settings and it will disable the network conference feature, previously once it was enabled on yealink phones it could not be disabled without manually changing it in the phone or a factory default.
There was an illogical if/else statement that the "else" condition would always set a null value, so it didn't really matter. Re-wrote it to properly filter if the transport is set to dns srv and not affix the SIP Port to the server address.
