[FIX] registry: avoid discarding registry or cache when the registry is fresh

When the sequence value is 1 it means that either:
 - the registry was just instantiated, so there is no
   reason to reload it immediately, the real checks will
   start at next request
 - the db was just created with new sequences set to 1,
   so there has been no change to reload

In both cases there is no good reason to reload the
registry, and it is actually a performance killer,
especially for cron workers that keep iterating on
the list of databases.
[FIX] registry: restore `elif` changed to `if` in previous commit, for better readability (no effect)

This should have no effect because when the first `if`
is entered a new registry is instantiated with
the default value for base_cache_signaling_sequence
set to 1, preventing entering the next `if` even
without `elif`.