Add missing documentation on return of snmp_facts (#35101)

The snmp_facts module lacked any information on what kind
of data can be expected on the return of successful execution.

This patch expands the docs to included info on return output
including sample data and full descriptions.

Signed-off-by: Eric Brown <browne@vmware.com>

lib/ansible/modules/net_tools/snmp_facts.py

@@ -87,6 +87,82 @@ EXAMPLES = '''
   delegate_to: localhost
 '''
 
+RETURN = '''
+ansible_sysdescr:
+  description: A textual description of the entity.
+  returned: success
+  type: string
+  sample: Linux ubuntu-user 4.4.0-93-generic #116-Ubuntu SMP Fri Aug 11 21:17:51 UTC 2017 x86_64
+ansible_sysobjectid:
+  description: The vendor's authoritative identification of the network management subsystem contained in the entity.
+  returned: success
+  type: string
+  sample: 1.3.6.1.4.1.8072.3.2.10
+ansible_sysuptime:
+  description: The time (in hundredths of a second) since the network management portion of the system was last re-initialized.
+  returned: success
+  type: int
+  sample: 42388
+ansible_syscontact:
+  description: The textual identification of the contact person for this managed node, together with information on how to contact this person.
+  returned: success
+  type: string
+  sample: Me <me@example.org>
+ansible_sysname:
+  description: An administratively-assigned name for this managed node.
+  returned: success
+  type: string
+  sample: ubuntu-user
+ansible_syslocation:
+  description: The physical location of this node (e.g., `telephone closet, 3rd floor').
+  returned: success
+  type: string
+  sample: Sitting on the Dock of the Bay
+ansible_all_ipv4_addresses:
+  description: List of all IPv4 addresses.
+  returned: success
+  type: list
+  sample: ["127.0.0.1", "172.17.0.1"]
+ansible_interfaces:
+  description: Dictionary of each network interface and its metadata.
+  returned: success
+  type: dict
+  sample: {
+    "1": {
+        "adminstatus": "up",
+        "description": "",
+        "ifindex": "1",
+        "ipv4": [
+            {
+                "address": "127.0.0.1",
+                "netmask": "255.0.0.0"
+            }
+        ],
+        "mac": "",
+        "mtu": "65536",
+        "name": "lo",
+        "operstatus": "up",
+        "speed": "65536"
+    },
+    "2": {
+        "adminstatus": "up",
+        "description": "",
+        "ifindex": "2",
+        "ipv4": [
+            {
+                "address": "192.168.213.128",
+                "netmask": "255.255.255.0"
+            }
+        ],
+        "mac": "000a305a52a1",
+        "mtu": "1500",
+        "name": "Intel Corporation 82545EM Gigabit Ethernet Controller (Copper)",
+        "operstatus": "up",
+        "speed": "1500"
+    }
+  }
+'''
+
 import binascii
 from collections import defaultdict