alarms, billing: fix liquibase character varying and cleanup

Applied https://rb.dcache.org/r/6952 (with adjustments)

see also

Committed: 460b9e0ed64f2c8d83a738471b28700e71a698f7
Merge-req: https://github.com/dCache/dcache/pull/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'.