ci: Drop P8 mambo from Debian unstable

Debian Unstable has removed OpenSSL 1.0.0 from the repository so mambo
no longer runs:

  /opt/ibm/systemsim-p8/bin/systemsim-pegasus: error while loading shared
  libraries: libcrypto.so.1.0.0: cannot open shared object file: No such
  file or directory

By removing it from the container these tests will be automatically
skipped.

Tracked in open-power/op-build#2519

Signed-off-by: Joel Stanley <joel@jms.id.au>
Signed-off-by: Stewart Smith <stewart@linux.ibm.com>

opal-ci/Dockerfile-debian-unstable

@@ -3,7 +3,6 @@ ENV DEBIAN_FRONTEND    noninteractive
 RUN if [ `arch` != "ppc64le" ]; then apt-get update -qq && apt-get install -y gcc-powerpc64le-linux-gnu; fi
 RUN apt-get update -qq && apt-get install -y gcc-arm-linux-gnueabi || true
 RUN apt-get update -qq && apt-get install -y gcc ccache expect libssl-dev wget curl xterm device-tree-compiler build-essential gcc python g++ pkg-config libz-dev libglib2.0-dev libpixman-1-dev libfdt-dev git libstdc++6 valgrind libtcl8.6 clang qemu-system-ppc
-RUN if [ `arch` = "x86_64" ]; then curl -L -O http://public.dhe.ibm.com/software/server/powerfuncsim/p8/packages/v1.0-2/systemsim-p8_1.0-2_amd64.deb; dpkg -i systemsim-p8_1.0-2_amd64.deb; fi
 RUN if [ `arch` = "x86_64" ]; then curl -O http://public.dhe.ibm.com/software/server/powerfuncsim/p9/packages/v1.1-0/systemsim-p9-1.1-0-trusty_amd64.deb; dpkg -i systemsim-p9-1.1-0-trusty_amd64.deb; fi
 COPY . /build/
 WORKDIR /build