redhat_subscription: fix activationkeys argument

Prior to this commit, Ansible would pass '--activationkeys <value>' as a
literal string, which the remote server would interpret as a single
argument to subscription-manager.

This led to the following failure message when using an activation key:

  subscription-manager: error: no such option: --activationkey "mykey"

Update the arguments so that the remote server will properly interpret
them as two separate values.

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

@@ -207,7 +207,7 @@ class Rhsm(RegistrationBase):
 
         # Generate command arguments
         if activationkey:
-            args.append('--activationkey "%s"' % activationkey)
+            args.extend(['--activationkey', activationkey])
         else:
             if autosubscribe:
                 args.append('--autosubscribe')