Several tests were corrupting Kryo which was then returned to the common pool. (#378)

* We were leaving trailing attachmentStorage on pooled kryo instances after some tests.  Changed attachment storage logic to make it impossible to leave it behind.

* Some low level tests corrupt the Kryo config, so do not return to pool when this is the case.  Also, we discovered that Kryo is caching class name to class resolution.  We don't want to do this where attachments are involved.  The errors raised highlighted a class missing from the whitelist.  Need to write a unit test to test the class loader issue.

* Unit test for attachment class loading with kryo.

node/src/main/kotlin/net/corda/node/serialization/DefaultWhitelist.kt

@@ -6,6 +6,7 @@ import net.corda.core.node.CordaPluginRegistry
 import net.corda.core.serialization.SerializationCustomization
 import org.apache.activemq.artemis.api.core.SimpleString
 import rx.Notification
+import rx.exceptions.OnErrorNotImplementedException
 import java.math.BigDecimal
 import java.time.LocalDate
 import java.time.Period
@@ -49,6 +50,7 @@ class DefaultWhitelist : CordaPluginRegistry() {
             addToWhitelist(LocalDate::class.java)
             addToWhitelist(Period::class.java)
             addToWhitelist(BitSet::class.java)
+            addToWhitelist(OnErrorNotImplementedException::class.java)
         }
         return true
     }