openjdk: revert to a semi-manual installation

Unfortunately, using package-installs means there is no way to set the
proper openjdk package depending on the version of the distro, and so
far it is hardcoded to 7. On Fedora >= 21, the default openjdk is 8, and
due to bugs in yum [1] this has not caused build errors so far, but
leaving a java-less image.

The chosen solution is to not use package-installs anymore, still using
pkg-map (called manually) to give the right name for the built distro.
The default is still set to install openjdk v7 everywhere, as before;
as drawback, building images based on Fedora >= 21 (which is the default
in diskimage-builder since version 0.1.43) will fail hard now.

[1] like not exiting when asking to install non-existing packages if
specified together with existing ones

Change-Id: I53195daa8d29b15dcae548eb76c5c9efb6ad50ef

elements/openjdk/element-deps

@@ -1,2 +1,2 @@
 java
-package-installs
+pkg-map

elements/openjdk/install.d/33-java

@@ -8,6 +8,22 @@ set -o pipefail
 
 echo "Installing OpenJDK"
 
+default_jdk_version_for_distro () {
+    case "$DISTRO_NAME" in
+        centos | fedora | rhel | ubuntu )
+            echo "7"
+        ;;
+        *)
+            echo "Unknown OpenJDK distro: $DISTRO_NAME" >&2
+            exit 1
+        ;;
+    esac
+}
+
+pkg=openjdk-$(default_jdk_version_for_distro)
+pkg=$(pkg-map --element openjdk $pkg)
+install-packages $pkg
+
 case "$DISTRO_NAME" in
     ubuntu )
         JRE_PATH=$(update-alternatives --list java)

elements/openjdk/package-installs.yaml

@@ -1 +0,0 @@
-openjdk-7: