the ssh shared module will try to use keys if the password is not supplied

The current ssh shared module forces only password based authentication.  This
change will allow the ssh module to use keys if a password is not provided.

lib/ansible/module_utils/ssh.py

@@ -91,12 +91,17 @@ class Ssh(object):
     def __init__(self):
         self.client = None
 
-    def open(self, host, port=22, username=None, password=None, timeout=10):
+    def open(self, host, port=22, username=None, password=None,
+            timeout=10, key_filename=None):
+
         ssh = paramiko.SSHClient()
         ssh.set_missing_host_key_policy(paramiko.AutoAddPolicy())
 
+        use_keys = password is None
+
         ssh.connect(host, port=port, username=username, password=password,
-                    timeout=timeout, allow_agent=False, look_for_keys=False)
+                    timeout=timeout, allow_agent=use_keys, look_for_keys=use_keys,
+                    key_filename=key_filename)
 
         self.client = ssh
         return self.on_open()