Make state exists universal in collection (#13890)

Make state: exists available for all API modules

Make state:exists return the ID just like it would if it created the resource

awx_collection/tests/integration/targets/schedule/tasks/main.yml

@@ -76,6 +76,42 @@
         that:
           - result is changed
 
+    - name: Build a real schedule with exists
+      schedule:
+        name: "{{ sched1 }}"
+        state: exists
+        unified_job_template: "Demo Job Template"
+        rrule: "DTSTART:20191219T130551Z RRULE:FREQ=WEEKLY;INTERVAL=1;COUNT=1"
+      register: result
+
+    - assert:
+        that:
+          - result is not changed
+
+    - name: Delete a real schedule
+      schedule:
+        name: "{{ sched1 }}"
+        state: absent
+        unified_job_template: "Demo Job Template"
+        rrule: "DTSTART:20191219T130551Z RRULE:FREQ=WEEKLY;INTERVAL=1;COUNT=1"
+      register: result
+
+    - assert:
+        that:
+          - result is changed
+
+    - name: Build a real schedule with exists
+      schedule:
+        name: "{{ sched1 }}"
+        state: exists
+        unified_job_template: "Demo Job Template"
+        rrule: "DTSTART:20191219T130551Z RRULE:FREQ=WEEKLY;INTERVAL=1;COUNT=1"
+      register: result
+
+    - assert:
+        that:
+          - result is changed
+
     - name: Rebuild the same schedule
       schedule:
         name: "{{ sched1 }}"