pgsql: Report correct name in autovacuum "work items" activity

Report correct name in autovacuum "work items" activity

We were reporting the database name instead of the relation name to
pg_stat_activity.  Repair.

Reported-by: Justin Pryzby
Discussion: https://postgr.es/m/20190220185552.GR28750@telsasoft.com

Branch
------
REL_11_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/630de1131dca80fd63cecfbe6a14b8a5b405b434

Modified Files
--------------
src/backend/postmaster/autovacuum.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)