Fix Dendrite extra arguments getting lost

Move the `matrix_dendrite_process_extra_arguments` line up so it doesn't get lost, and add a trailing backslash

roles/matrix-dendrite/templates/dendrite/systemd/matrix-dendrite.service.j2

@@ -46,13 +46,13 @@ ExecStart={{ matrix_host_command_docker }} run --rm --name matrix-dendrite \
 			{% endfor %}
 			{{ matrix_dendrite_docker_image }} \
 			-config /data/dendrite.yaml \
+			{{ matrix_dendrite_process_extra_arguments|join(' ') }} \
 			{% if matrix_dendrite_http_bind_address %}
 			-http-bind-address {{ matrix_dendrite_http_bind_address }}
 			{% endif %}
 			{% if matrix_dendrite_https_bind_address %}
 			-https-bind-address {{ matrix_dendrite_https_bind_address }}
 			{% endif %}
-			{{ matrix_dendrite_process_extra_arguments|join(' ') }}
 
 ExecStop=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} kill matrix-dendrite 2>/dev/null || true'
 ExecStop=-{{ matrix_host_command_sh }} -c '{{ matrix_host_command_docker }} rm matrix-dendrite 2>/dev/null || true'