openjdk: install openjdk 8 for fedora >= 21

There is no more openjdk 7 available there, so install openjdk 8 which
is the default.

Change-Id: I934448b0abb5ee62ab24d019ac29977837326178

elements/openjdk/install.d/33-java

@@ -10,9 +10,16 @@ echo "Installing OpenJDK"
 
 default_jdk_version_for_distro () {
     case "$DISTRO_NAME" in
-        centos | fedora | rhel | ubuntu )
+        centos | rhel | ubuntu )
             echo "7"
         ;;
+        fedora )
+            if [ $(lsb_release -rs) -ge '21' ]; then
+                echo "8"
+            else
+                echo "7"
+            fi
+        ;;
         *)
             echo "Unknown OpenJDK distro: $DISTRO_NAME" >&2
             exit 1