ios_facts: Strip header from running-config (#48047)

IOS prepends a show running-config with lines that are not part of the
configuration, keeping the output from being an entirely valid configuration:
R1#show run
Building configuration...

Current configuration : 2045 bytes
...

In order to be able to use the config from ios_facts as-is, strip this
header.

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

@@ -282,6 +282,9 @@ class Config(FactsBase):
         super(Config, self).populate()
         data = self.responses[0]
         if data:
+            data = re.sub(
+                r'^Building configuration...\s+Current configuration : \d+ bytes\n',
+                '', data, flags=re.MULTILINE)
             self.facts['config'] = data