AMQP-783: Allow blank key/trust store passwords

JIRA: https://jira.spring.io/browse/AMQP-783

**Cherry-pick to 1.7.x**

# Conflicts:
#	spring-rabbit/src/main/java/org/springframework/amqp/rabbit/connection/RabbitConnectionFactoryBean.java

Author: zadeluca

spring-rabbit/src/main/java/org/springframework/amqp/rabbit/connection/RabbitConnectionFactoryBean.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2002-2016 the original author or authors.
+ * Copyright 2002-2017 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -69,6 +69,7 @@
  * @author Arnaud Cogoluègnes
  * @author Hareendran
  * @author Artem Bilan
+ * @author Zachary DeLuca
  *
  * @since 1.4
  */
@@ -636,11 +637,11 @@ protected void setUpSSL() throws Exception {
 			String keyStoreType = getKeyStoreType();
 			String trustStoreType = getTrustStoreType();
 			char[] keyPassphrase = null;
-			if (StringUtils.hasText(keyStorePassword)) {
+			if (keyStorePassword != null) {
 				keyPassphrase = keyStorePassword.toCharArray();
 			}
 			char[] trustPassphrase = null;
-			if (StringUtils.hasText(trustStorePassword)) {
+			if (trustStorePassword != null) {
 				trustPassphrase = trustStorePassword.toCharArray();
 			}
 			KeyManager[] keyManagers = null;