Fix rollback in junos_config (#31424)

* Fix rollback in junos_config

Fixes #30778

*  Call `load_configuration` with rollback id in case
   the id is given as input
*  Pass rollback id to `get_diff()` to fetch diff from device

* Fix unit test

test/integration/targets/junos_config/tests/netconf/single.yaml

@@ -41,6 +41,37 @@
     that:
       - "result.changed == true"
 
+- name: teardown for rollback test
+  junos_config:
+    lines:
+    - delete system syslog file test1
+    provider: "{{ netconf }}"
+
+- name: Configure syslog file
+  junos_config:
+    lines:
+    - set system syslog file test1 any any
+    provider: "{{ netconf }}"
+  register: result
+
+- assert:
+    that:
+      - "result.changed == true"
+      - result.diff.prepared | search("\+ *file test1")
+      - result.diff.prepared | search("\+ *any any")
+
+- name: Rollback junos config
+  junos_config:
+    rollback: 1
+    provider: "{{ netconf }}"
+  register: result
+
+- assert:
+    that:
+      - "result.changed == true"
+      - result.diff.prepared | search("\+ *file test1")
+      - result.diff.prepared | search("\+ *any any")
+
 - name: teardown
   junos_config:
     lines: