(doc) issue warnings to certificate does't match

issue warnings when certificate between master and agent doesn't match.
At the moment the message says to execute rm -r certificate but it doesn't solve the problem, need to erase the private key too.
This code shows the right command to execute.
to test this erase your certificate and key from the agent using the command below and try use puppet agent -t again.
find $(puppet master --configprint ssldir) `facter fqdn`.pem -delete
(doc) more specific warning for certificate matching issues

This adds a bit more information on commands to run, in particular with
the addition of how to delete the cert on windows agents.
Merge branch 'patch-1'

* patch-1:
  (doc) more specific warning for certificate matching issues
  (doc) issue warnings to certificate does't match