Don't install python-software-properties on Ubuntu 18.04+
Don't install python-software-properties on Ubuntu 18.04+

This package was last shipped with Ubuntu artful (17.10).

To test this, one can use the following Dockerfile. Before this change
the installation failed:

    FROM ubuntu:18.04
    COPY easy/install.sh /install.sh
    RUN chmod +x /install.sh && \
        apt-get update && \
        apt-get install -y wget gnupg2 openjdk-8-jdk-headless && \
        /install.sh

crate/crate-utils,crate/crate-utils