update dockerfile (#4164)

frameworks/Java/smart-socket/smart-socket.dockerfile

@@ -1,10 +1,10 @@
-FROM maven:3.5.3-jdk-10-slim as maven
+FROM maven:3.5.3-jdk-8-slim as maven
 WORKDIR /smart-socket
 COPY pom.xml pom.xml
 COPY src src
 RUN mvn compile assembly:single -q
 
-FROM openjdk:10-jre-slim
+FROM openjdk:8-jre-slim
 WORKDIR /smart-socket
 COPY --from=maven /smart-socket/target/smart-socket-benchmark-1.0-jar-with-dependencies.jar app.jar
 CMD ["java", "-server", "-XX:+UseNUMA", "-XX:+UseParallelGC", "-XX:+AggressiveOpts", "-cp", "app.jar", "org.smartboot.http.Bootstrap"]