Modules: initialize shared dict state entry expiration

Modules: initialize shared dict state entry expiration

When a shared dict state entry omits the optional expire field, its
expiration remains uninitialized.  In a zone with timeout=, the entry
can be discarded as expired or loaded with an arbitrary expiration
instead of receiving the zone timeout.

Initialize expiration to zero before parsing the entry so an omitted
expire field is treated like an explicit zero.  The entry then receives
the zone timeout and the state file is scheduled for saving.