1121674: Persist new entitlements to the database before post-ent

The source entitlement was getting an ID set when it was flushed
at a random point (because it was added to pool and consumer).
This didn't always occur before we needed to read the entitlement
ID in order to create a SourceSubscription entry with ent.id as
subkey
Merge pull request #648 from candlepin/ckozak/bind_transient_value_exc

1121674: Persist new entitlements to the database before post-ent