gitea: fix bugs with auto upgrade

roles/gitea/tasks/install.yaml

@@ -10,3 +10,4 @@
   notify:
     - restart gitea
   retries: 3
+  when: gitea_version != gitea_local_version

roles/gitea/tasks/pre.yaml

@@ -6,7 +6,7 @@
 
 - name: set gitea_installed
   set_fact:
-    gitea_installed: st.stat.exists
+    gitea_installed: "{{ st.stat.exists | bool }}"
 
 - block:
   - name: determine latest version
@@ -36,7 +36,7 @@
 - name: set gitea_local_version to 0
   set_fact:
     gitea_local_version: "0"
-  when: not gitea_installed | bool
+  when: not (gitea_installed | bool)
 
 - block:
   - name: get checksums