fix(model-server): properly handle signals in the docker container

Use exec in the model-server launcher script used in the Docker image to
ensure that SIGTERM etc. reach the started java process. Otherwise,
Ctrl-C cannot be used to terminate the docker container and k8s will
have to resort to killing instead of graceful shutdown.

Author: languitar

model-server/run-model-server.sh

@@ -1,3 +1,3 @@
 #!/bin/sh
 
-java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5071 -XX:MaxRAMPercentage=75 -Djdbc.url=$jdbc_url -cp "model-server/build/libs/*" org.modelix.model.server.Main "$@"
+exec java -agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5071 -XX:MaxRAMPercentage=75 -Djdbc.url=$jdbc_url -cp "model-server/build/libs/*" org.modelix.model.server.Main "$@"