puppet: make arg puppetmaster optional

puppetmaster was used to determine if `agent` or `apply` should be used. But puppetmaster is not required by puppet per default. Puppet may have a config or could find out by itself (...) where the puppet master is.

It changed the code so we only use `apply` if a manifest was passed, otherwise we use `agent`.

This also fixes the example, which did not work the way without this change.

~~~
# Run puppet agent and fail if anything goes wrong
- puppet
~~~

system/puppet.py

@@ -35,12 +35,12 @@ options:
     default: 30m
   puppetmaster:
     description:
-      - The hostname of the puppetmaster to contact. Must have this or manifest
+      - The hostname of the puppetmaster to contact.
     required: false
     default: None
   manifest:
     desciption:
-      - Path to the manifest file to run puppet apply on. Must have this or puppetmaster
+      - Path to the manifest file to run puppet apply on.
     required: false
     default: None
   show_diff:
@@ -69,7 +69,7 @@ author: Monty Taylor
 '''
 
 EXAMPLES = '''
-# Run puppet and fail if anything goes wrong
+# Run puppet agent and fail if anything goes wrong
 - puppet
 
 # Run puppet and timeout in 5 minutes
@@ -115,7 +115,7 @@ def main():
             environment=dict(required=False, default=None),
         ),
         supports_check_mode=True,
-        required_one_of=[
+        mutually_exclusive=[
             ('puppetmaster', 'manifest'),
         ],
     )
@@ -135,7 +135,7 @@ def main():
                     manifest=p['manifest']))
 
     # Check if puppet is disabled here
-    if p['puppetmaster']:
+    if not p['manifest']:
         rc, stdout, stderr = module.run_command(
             PUPPET_CMD + " config print agent_disabled_lockfile")
         if os.path.exists(stdout.strip()):
@@ -154,13 +154,14 @@ def main():
     base_cmd = "timeout -s 9 %(timeout)s %(puppet_cmd)s" % dict(
         timeout=pipes.quote(p['timeout']), puppet_cmd=PUPPET_CMD)
 
-    if p['puppetmaster']:
+    if not p['manifest']:
         cmd = ("%(base_cmd)s agent --onetime"
-               " --server %(puppetmaster)s"
                " --ignorecache --no-daemonize --no-usecacheonfailure --no-splay"
                " --detailed-exitcodes --verbose") % dict(
                    base_cmd=base_cmd,
-                   puppetmaster=pipes.quote(p['puppetmaster']))
+                   )
+        if p['puppetmaster']:
+            cmd += " -- server %s" % pipes.quote(p['puppetmaster'])
         if p['show_diff']:
             cmd += " --show-diff"
         if p['environment']: