Update launch script integration tests

- Use the latest Docker image for Ubuntu 14.04 LTS based tests
- Add Ubuntu 16.04 LTS based tests

Closes gh-5868

spring-boot-integration-tests/spring-boot-launch-script-tests/src/test/resources/conf/Ubuntu/trusty-20160503.1/Dockerfile

+FROM ubuntu:trusty-20160503.1
+RUN apt-get update && \
+    apt-get install -y software-properties-common && \
+    add-apt-repository ppa:webupd8team/java -y && \
+    apt-get update && \
+    echo oracle-java7-installer shared/accepted-oracle-license-v1-1 select true | /usr/bin/debconf-set-selections && \
+    apt-get install -y oracle-java8-installer && \
+    apt-get install -y curl && \
+    apt-get clean

spring-boot-integration-tests/spring-boot-launch-script-tests/src/test/resources/conf/Ubuntu/trusty-20160317/Dockerfile → spring-boot-integration-tests/spring-boot-launch-script-tests/src/test/resources/conf/Ubuntu/xenial-20160503/Dockerfile

-FROM ubuntu:trusty-20160317
-RUN apt-get install -y software-properties-common && \
+FROM ubuntu:xenial-20160503
+RUN apt-get update && \
+    apt-get install -y software-properties-common && \
     add-apt-repository ppa:webupd8team/java -y && \
     apt-get update && \
     echo oracle-java7-installer shared/accepted-oracle-license-v1-1 select true | /usr/bin/debconf-set-selections && \