Don't store state in InMemoryAuditLogHandlerResourceDefinition

https://github.com/wildfly/wildfly-core/pull/890#discussion_r35354989

private static final Map<String, InMemoryAuditLogHander> histories = Collections.synchronizedMap(new HashMap<String, InMemoryAuditLogHander>());

We don't want to delay merging this PR for this, but once it's merged please send up a PR to make this a non-static field and have the InMemoryAuditLogHandlerResourceDefinition pass a ref to it to the handlers when it constructs them.

Having this be static is no big deal in this case, but I don't want anyone looking at kernel code and thinking that using static fields to store state is a good practice.