weblogic 12c: stopping nodemanager without killing managed server

Question

We are using weblogic 12c, and we have a managed server named app1 on our application server. We would like to stop and restart nodemanager to rotate the ssl certificate that we use for nodemanager. However, whenever we use the $DOMAIN_HOME/bin/stopNodeManager.sh or call stopNodeManager() from wlst, it also kills app1 along with nodemanager.

1. Is there some configuration setting that is causing the app1 managed server to go down and startup with nodemanager? If so, what is it?
2. is there some other way to take down nodemanager without the app1 managed server also being shutdown?