Merge pull request #44 from kemitix/docker-openjdk-8-already-installed

Don't install openjdk
diff --git a/Dockerfile b/Dockerfile
index de7ac9b..226314a 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -17,7 +17,7 @@
 
 # For all Brooklyn, we use a debian distribution instead of alpine as there are some libgcc incompatibilities with GO
 # and PhantomJS
-FROM maven:3.6.3-jdk-8
+FROM maven:3.5.4-jdk-8
 
 # Install necessary binaries to build brooklyn
 # Strictly speaking, rsync, gpg, tar, and zip are only necessary