Create uprConnMap before EventuallyPersistentStore is initialized

When EventuallyPersistent store is initialized it creates a job
that will persist engine stats periodically. As a result we need
to make sure an uprConnMap exists before creating the
EventuallyPersistentStore so that the stats tap call won't cause
a crash.

Change-Id: I496053ac3fb3f4ecae15ed20847ca640ab87c03c
Reviewed-on: http://review.couchbase.org/29908
Reviewed-by: Sundararaman Sridharan <sundar.sridharan@gmail.com>
Reviewed-by: David Liao <david.liao@couchbase.com>
Tested-by: Michael Wiederhold <mike@couchbase.com>