add example using the "when" keyword (#41038)

* add example using the "when" keyword

<!--- Your description here -->
add example using the "when" keyword comparing group_var variable to returned value from ios_facts
+label: docsite_pr
+label: issue #311

* Update ios_config.py

* Update ios_config.py

lib/ansible/modules/network/ios/ios_config.py

@@ -272,6 +272,16 @@ EXAMPLES = """
       - shutdown
     # parents: int gig1/0/11
     parents: interface GigabitEthernet1/0/11
+
+# Set boot image based on comparison to a group_var (version) and the version
+# that is returned from the `ios_facts` module
+- name: SETTING BOOT IMAGE
+  ios_config:
+    lines:
+      - no boot system
+      - boot system flash bootflash:{{new_image}}
+    host: "{{ inventory_hostname }}"
+  when: ansible_net_version != version
 """
 
 RETURN = """