Fix type of the rhn_register module

Password and activationkey should be tagged as no_log, as they
are supposed to be secret.
sslcacert is a path, so should be tagged as such.

lib/ansible/modules/packaging/os/rhn_register.py

@@ -307,11 +307,11 @@ def main():
                 argument_spec = dict(
                     state = dict(default='present', choices=['present', 'absent']),
                     username = dict(default=None, required=False),
-                    password = dict(default=None, required=False),
+                    password = dict(default=None, required=False, no_log=True),
                     server_url = dict(default=rhn.config.get_option('serverURL'), required=False),
-                    activationkey = dict(default=None, required=False),
+                    activationkey = dict(default=None, required=False, no_log=True),
                     profilename = dict(default=None, required=False),
-                    sslcacert = dict(default=None, required=False),
+                    sslcacert = dict(default=None, required=False, type='path'),
                     systemorgid = dict(default=None, required=False),
                     enable_eus = dict(default=False, type='bool'),
                     channels = dict(default=[], type='list'),