factory: fix getBlockingHistory implementation

To find all service change events for a given account, we cannot simply
look at SERVICE_STATE_CHANGE subscription events. For example, if an
overdue transition forces a block billing state, the subscription
event type will be PAUSE_BILLING.

Instead, we need to look for all events besides entitlement ones.

This should fix part of killbill/killbill-analytics-plugin#17.

Signed-off-by: Pierre-Alexandre Meyer <pierre@ning.com>