fix: remove systemd on docker-based installations

The systemd package was installed by default for some reason, causing issues when interacting with init processes. Specifically, we would detect systemctl on runit systems and incorrectly invoke that when restarting processes.

Additionally, ensure the copied binaries are executable.

Closes #7089

Dockerfile

@@ -20,6 +20,7 @@ SHELL ["/bin/bash", "-o", "pipefail", "-c"]
 # hadolint ignore=DL3005,DL3008
 RUN mkdir -p /etc/apt/keyrings \
   && mkdir -p /etc/apt/keyrings \
+  && apt-get remove -y systemd && apt-get autoremove -y && apt-get update && apt-get install -y --no-install-recommends gpg lsb-release \
   && curl -fsSL https://download.docker.com/linux/ubuntu/gpg | gpg --dearmor -o /etc/apt/keyrings/docker.gpg \
   && echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] https://download.docker.com/linux/ubuntu $(lsb_release -cs) stable" | tee /etc/apt/sources.list.d/docker.list > /dev/null \
   && apt-get update \
@@ -45,6 +46,7 @@ COPY ./docker .
 
 RUN \
   rsync -a /tmp/ / \
+  && chmod +x /usr/local/bin/* \
   && rm -rf /tmp/* \
   && rm /etc/runit/runsvdir/default/sshd/down \
   && chown -R dokku:dokku /home/dokku/ \
@@ -59,7 +61,6 @@ RUN \
   && ln -sf /mnt/dokku/var/lib/dokku/data /var/lib/dokku/data \
   && ln -sf /mnt/dokku/var/lib/dokku/services /var/lib/dokku/services \
   && mv /etc/my_init.d/00_regen_ssh_host_keys.sh /etc/my_init.d/15_regen_ssh_host_keys \
-  && rm -f /usr/bin/systemctl \
   && rm -f /etc/nginx/sites-enabled/default /usr/share/nginx/html/index.html /etc/my_init.d/10_syslog-ng.init \
   && rm -f /usr/local/openresty/nginx/conf/sites-enabled/default /usr/share/openresty/html/index.html \
   && sed -i '/imklog/d' /etc/rsyslog.conf \