Fix uncommenting of config value

The old regex did change the value of the cgroup_manager config, but not
uncomment it, resulting in a useless change. This patch should uncomment
it now as well.

Dockerfile

@@ -8,7 +8,7 @@ RUN true\
    && dnf -y upgrade \
    && dnf -y install podman buildah findutils git \
    && dnf clean all \
-   && sed -e 's/cgroup_manager =.*/cgroup_manager = "cgroupfs"/' /usr/share/containers/containers.conf > /etc/containers/containers.conf \
+   && sed -e 's/.* cgroup_manager =.*/cgroup_manager = "cgroupfs"/' /usr/share/containers/containers.conf > /etc/containers/containers.conf \
    && git clone -b "$SI_TOOLS_VERSION" --depth=3 https://git.shivering-isles.com/shivering-isles/shell-tools.git ./shell-tools \
    && ./shell-tools/install.sh \
    && rm -rf ./shell-tools \