flux-accounting DB: update schema version

Problem: The schema for the flux-accounting DB has been changed as a
result of flux-framework#357.

Update the schema version for the flux-accounting DB in __init__.py.in
and in the front-end flux-account-service.py script.

src/bindings/python/fluxacct/accounting/__init__.py.in

@@ -1,5 +1,5 @@
 db_dir = "@X_LOCALSTATEDIR@/lib/flux/"
 db_path = "@X_LOCALSTATEDIR@/lib/flux/FluxAccounting.db"
-db_schema_version = 20
+db_schema_version = 21
 
 __all__ = ["db_dir", "db_path", "db_schema_version"]

src/cmd/flux-account-service.py

@@ -519,7 +519,7 @@ def main():
     cur = conn.cursor()
     cur.execute("PRAGMA user_version")
     db_version = cur.fetchone()[0]
-    if db_version < 20:
+    if db_version < 21:
         LOGGER.error(
             "flux-accounting database out of date; please update DB with 'flux account-update-db' before running commands"
         )