alarms, billing: fix liquibase character varying and cleanup

Applied https://rb.dcache.org/r/6952 (with adjustments)

see also

Committed: 460b9e0
Merge-req: dCache#517

RELEASE NOTES:  fixes a regression in liquibase scripts for alarms and billing
due to a bug in updated version (3.x) producing incorrect SQL for 'character varying'.
Merge pull request #707 from alrossi/fix/2.8/alarms_billing_varchar

alarms, billing: fix liquibase character varying and cleanup