spacemanager: Fix database sequence initialization

The default range for sequences starts at 1. This caused failures
with the schema changeset when migrating from a database where the
largest id was smaller than 1.

Target: trunk
Request: 2.8
Require-notes: yes
Require-book: no
Acked-by: Paul Millar <paul.millar@desy.de>
Patch: http://rb.dcache.org/r/6711/
(cherry picked from commit e3ac8f69bd2e42b33066d169b6dd7ff95f476a6e)
Merge pull request #460 from gbehrmann/fix/2.8/rb6711

spacemanager: Fix database sequence initialization