Use java version independent package on Ubuntu

Different versions of Ubuntu ship with different versions of Java.
Trusty had 7, Xenial has 8, and so on. This causes problems when we
hardcode a versioned package name into our dep lists as that version may
not exist everywhere. Thankfully Ubuntu provides a default-jre-headless
package that we can use instead that maps properly onto whatever java
version is correct.

Change-Id: I4e5da215c8f7aa426494686d5043995ce5d3c3af

files/debs/general

@@ -2,6 +2,7 @@ bc
 bridge-utils
 bsdmainutils
 curl
+default-jre-headless  # NOPRIME
 g++
 gcc
 gettext  # used for compiling message catalogs
@@ -17,7 +18,6 @@ libxml2-dev  # lxml
 libxslt1-dev  # lxml
 libyaml-dev
 lsof # useful when debugging
-openjdk-7-jre-headless  # NOPRIME
 openssh-server
 openssl
 pkg-config

pkg/elasticsearch.sh

@@ -83,7 +83,7 @@ function install_elasticsearch {
         return
     fi
     if is_ubuntu; then
-        is_package_installed openjdk-7-jre-headless || install_package openjdk-7-jre-headless
+        is_package_installed default-jre-headless || install_package default-jre-headless
 
         sudo dpkg -i ${FILES}/elasticsearch-${ELASTICSEARCH_VERSION}.deb
         sudo update-rc.d elasticsearch defaults 95 10