packaging: Dont use /etc/java/java.conf

The JAVA_HOME environment variable is defined in the history_service.sh
script, and comes from /etc/sysconfig/ovirt-engine, so it is confusing
for users if we also get it from /etc/java/java.conf.

Change-Id: I4fc47a9e3b24d7a90a0ea919da53ec63144b9d86
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>