Fix AMQPS XML Validation

The Java client for Rabbit has [three different modes](https://www.rabbitmq.com/ssl.html#managers-and-stores) in which it can run AMQPS depending upon your desired security settings:

1. Without a trust store or a key store defined the client will accept any certificates presented by the server and will not give a client certificate
2. With a trust store but not a key store defined the client will check the remote certificate presented by the server but will not give a client certificate
3. With a trust store and a key store defined the client will both check the remote certificate presented by the server and will give a client certificate that is checked by the server against it's own trust store

As of right now you can successfully run the AMQP client in each of these configurations, however, if you choose to add a trust store to validate a remote certificate you must also add a blank element for the key store in order to get Mule Studio to pass XML schema validation. This merge fixes the XML schema validation issue and allows it to run without including misc. blank elements.

The following will work:
```
    <amqps:connector sslProtocol="SSLv3" name="AMQP_Connector" validateConnections="true" host="localhost" port="5671" virtualHost="/test" username="test" password="test" doc:name="AMQP Connector">
    </amqps:connector>
```
as will:
```
    <amqps:connector sslProtocol="SSLv3" name="AMQP_Connector" validateConnections="true" host="localhost" port="5671" virtualHost="/test" username="test" password="test" doc:name="AMQP Connector">
    	<amqps:ssl-key-store />
    	<amqps:ssl-trust-store path="messaging_trust_store.jks" type="JKS" algorithm="SunX509" storePassword="test"/>
    </amqps:connector>
```
However, this will not work without this merge patch:
```
    <amqps:connector sslProtocol="SSLv3" name="AMQP_Connector" validateConnections="true" host="localhost" port="5671" virtualHost="/test" username="test" password="test" doc:name="AMQP Connector">
    	<amqps:ssl-trust-store path="messaging_trust_store.jks" type="JKS" algorithm="SunX509" storePassword="test"/>
    </amqps:connector>
```