docker: use "--no-install-recommends" to reduce build time

Pass the flag "--no-install-recommends" to apt-get in order to trim down
the number of packages installed, both reducing build time and image
size. As this also causes some required packages to not be installed
anymore, add these explicitly to the set of packages installed.

azure-pipelines/docker/bionic

 ARG BASE
 FROM $BASE
 RUN apt-get update && \
-    apt-get install -y \
+    apt-get install -y --no-install-recommends \
         clang \
         cmake \
         curl \
+        gcc \
         git \
-        libcurl4 \
         libcurl4-openssl-dev \
+        libpcre3-dev \
         libssh2-1-dev \
         libssl-dev \
         libz-dev \
-        openjdk-11-jre-headless \
-        openssh-client \
+        make \
+        openjdk-8-jre-headless \
         openssh-server \
+        openssl \
         pkgconf \
+        python \
         valgrind \
         && \
     rm -rf /var/lib/apt/lists/*

azure-pipelines/docker/xenial

 ARG BASE
 FROM $BASE
 RUN apt-get update && \
-    apt-get install -y \
+    apt-get install -y --no-install-recommends \
         clang \
         cmake \
         curl \
+        gcc \
         git \
-        libcurl3 \
-        libcurl3-gnutls \
         libcurl4-gnutls-dev \
+        libpcre3-dev \
+        libssh2-1-dev \
         libssl-dev \
-        openjdk-8-jre \
-        openssh-client \
+        libz-dev \
+        make \
+        openjdk-8-jre-headless \
         openssh-server \
+        openssl \
         pkgconf \
+        python \
         valgrind \
         && \
     rm -rf /var/lib/apt/lists/*