fix(valkey): install systemd unit in proper dir; check local and git versions to avoid unnecessary recompiles

ansible_collections/nullified/infrastructure/roles/valkey/tasks/gather_facts.yml

@@ -1,7 +1,7 @@
 ---
 - name: find systemd unit directory
   become: true
-  ansible.builtin.command: pkg-config systemd --variable=systemdsystemunitdir
+  ansible.builtin.command: pkg-config systemd --variable=systemd_system_conf_dir
   changed_when: false
   register: systemd_unit_directory_cmd
 - name: find systemd version
@@ -10,7 +10,14 @@
     systemctl --version | awk '{if($1=="systemd" && $2~"^[0-9]+$"){print $2}}'
   changed_when: false
   register: systemd_version_cmd
+- name: find local valkey version
+  ansible.builtin.shell: >
+    valkey-cli --version | cut -d ' ' -f 2
+  failed_when: false
+  changed_when: false
+  register: valkey_local_version_cmd
 - name: set facts
   ansible.builtin.set_fact:
     systemd_unit_directory: "{{ systemd_unit_directory_cmd.stdout }}"
     systemd_version: "{{ systemd_version_cmd.stdout | int }}"
+    valkey_installed_version: "{{ (valkey_local_version_cmd.stdout_lines[0] | default('0')) if valkey_local_version_cmd.rc == 0 else '0' }}"