ios_facts: Fix minor aesthetical glitches (#46577)

* ios_facts: Fix LLDP gathering without neighbors

When LLDP is enabled but no neighbors are present, the following
structure is generated:
...
            "ansible_net_neighbors": {
                "null": [
                    {
                        "host": null,
                        "port": null
                    }
                ]
            },
...
If we are not able to find any relevant LLDP information, bail out early
so cases like shown above are handled more gracefully.

* ios_facts: Remove trailing space in lineprotocol

Some Cisco devices (at least CSR1000V 16.6.4) add a space after the
line protocol. This causes the space to be present in the result of
fact gathering:
            "ansible_net_interfaces": {
                "GigabitEthernet2": {
...
                    "lineprotocol": "up ",

Be more clear about scanning the output to avoid this behaviour.

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

@@ -382,6 +382,8 @@ class Interfaces(FactsBase):
             if entry == '':
                 continue
             intf = self.parse_lldp_intf(entry)
+            if intf is None:
+                return facts
             if intf not in facts:
                 facts[intf] = list()
             fact = dict()
@@ -447,7 +449,7 @@ class Interfaces(FactsBase):
             return match.group(1)
 
     def parse_lineprotocol(self, data):
-        match = re.search(r'line protocol is (.+)$', data, re.M)
+        match = re.search(r'line protocol is (\S+)\s*$', data, re.M)
         if match:
             return match.group(1)