pgsql: Fix vacuum_cost_delay check for balance calculation.

Fix vacuum_cost_delay check for balance calculation.

Commit 1021bd6a89 excluded autovacuum workers from cost-limit balance
calculations when per-relation options were set.  The code checks for
limit and cost_delay being greater than zero, but since cost_delay can
be set to -1 the test needs to check for greater than or zero.

Backpatch to all supported branches since 1021bd6a89 was backpatched
all the way at the time.

Author: Masahiko Sawada <sawada.mshk@gmail.com>
Reviewed-by: Melanie Plageman <melanieplageman@gmail.com>
Reviewed-by: Daniel Gustafsson <daniel@yesql.se>
Discussion: https://postgr.es/m/CAD21AoBS7o6Ljt_vfqPQPf67AhzKu3fR0iqk8B=vVYczMugKMQ@mail.gmail.com
Backpatch-through: v11 (all supported branches)

Branch
------
REL_14_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/0e8e5e856cc37cfcd8ac458dddd71f89d516fc27

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