MGMT-15809: change base image to stream9

Now that D/S building system fully supports RHEL-9 base images (and
allows easy installation of nmstate and other libs that were previously
unsupported) we can move U/S to stream9 and D/S to ubi9-minimal.

It doesn't seem possible to easily use ubi9-minimal U/S for the
assisted-service, because installation of nmstate packages either
requires entitlements running on a RHEL node, or alternatively an access
to RedHat's internal network (which can be a major problem for
U/S development). For a better consistency we're sticking with the same
for the agent, installer, etc.

Dockerfile.assisted_installer_agent

@@ -12,7 +12,7 @@ COPY . .
 
 RUN TARGETPLATFORM=$TARGETPLATFORM make build
 
-FROM quay.io/centos/centos:stream8
+FROM quay.io/centos/centos:stream9
 ARG TARGETPLATFORM
 RUN if [[ "$TARGETPLATFORM" == "linux/amd64" || -z "$TARGETPLATFORM" ]] ; then  dnf install -y biosdevname dmidecode ; fi
 RUN if [[ "$TARGETPLATFORM" == "linux/arm64" || -z "$TARGETPLATFORM" ]] ; then  dnf install -y dmidecode ; fi

subsystem/Dockerfile.agent_test

@@ -1,16 +1,19 @@
 ARG ASSISTED_INSTALLER_AGENT=quay.io/edge-infrastructure/assisted-installer-agent:latest
 FROM $ASSISTED_INSTALLER_AGENT
 
-RUN yum install -y yum-utils \
-    && yum-config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo \
-    && dnf install -y --nobest --allowerasing \
-    docker-ce \
-    docker-ce-cli \
-    containerd.io \
-    tcpdump \
-    procps \
-    python39 \
+# required due to issue https://github.com/docker/compose/issues/4060
+ENV LANG=C.UTF-8
+
+RUN dnf install -y 'dnf-command(config-manager)' && \
+    dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo && \
+    dnf install -y --nobest --allowerasing \
+        docker-ce \
+        docker-ce-cli \
+        containerd.io \
+        tcpdump \
+        procps \
+        python39 \
     && dnf clean all
 
 RUN echo -e "#!/bin/sh \nshift 7 && \$@" > /usr/bin/nsenter && chmod a+x /usr/bin/nsenter
-ADD podman_override /usr/bin/podman
+ADD podman_override /usr/bin/podman