Actually use matrix_synapse_storage_path

matrix_synapse_storage_path is already defined in matrix-synapse/defaults/main.yml (with a default of "{{ matrix_synapse_base_path }}/storage"), but was not being used for its presumed purpose in matrix-synapse.service.j2. As a result, if matrix_synapse_storage_path was overridden (in a vars.yml), the synapse service failed to start.

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

@@ -43,7 +43,7 @@ ExecStart=/usr/bin/docker run --rm --name matrix-synapse \
 			{% endif %}
 			-v {{ matrix_synapse_config_dir_path }}:/data:ro \
 			-v {{ matrix_synapse_run_path }}:/matrix-run:rw \
-			-v {{ matrix_synapse_base_path }}/storage:/matrix-media-store-parent:slave \
+			-v {{ matrix_synapse_storage_path }}:/matrix-media-store-parent:slave \
 			{% for volume in matrix_synapse_container_additional_volumes %}
 			-v {{ volume.src }}:{{ volume.dst }}:{{ volume.options }} \
 			{% endfor %}