ZOOKEEPER-3236: Upgrade BouncyCastle

Author: Colm O hEigeartaigh <coheigea@apache.org>

Reviewers: fangmin@apache.org, andor@apache.org

Closes #757 from coheigea/bouncycastle

pom.xml

@@ -276,7 +276,7 @@
     <json.version>1.1.1</json.version>
     <jline.version>2.11</jline.version>
     <kerby.version>1.1.0</kerby.version>
-    <bouncycastle.version>1.56</bouncycastle.version>
+    <bouncycastle.version>1.60</bouncycastle.version>
     <commons-collections.version>3.2.2</commons-collections.version>
     <commons-lang.version>2.6</commons-lang.version>
     <spotbugsannotations.version>3.1.9</spotbugsannotations.version>