Use of the <master> tag has been deprecated in c-turtle Since diamondback the tag gets ignored, it has no effect.
The <master> tag
This was the documentation when master was still a valid tag.
The <master> tag used to specify settings about the ROS Master, including allowing you to automatically start a master.
NOTE: <master> tags in included config files are ignored.
defines the behavior for starting a new master with the roslaunch session. If 'start', then a master will be started if none is running. If restart, then a fresh master will be started for the demo -- any existing master will be shutdown first. 'no' is the default behavior, which is to do nothing.