Fix flake pg_dump regression test

[fabriziomello]

Randomly we face problems executing pg_dump regression tests and the
commom failure is due to a DROP DATABASE.

Fixed id executing pg_terminate_backend over all active sessions for
the target database before issue the DROP DATABASE command.

[codecov]

Codecov Report

Merging #3636 (5da1787) into master (ef0ff45) will decrease coverage by 0.03%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #3636      +/-   ##
==========================================
- Coverage   90.82%   90.78%   -0.04%     
==========================================
  Files         212      212              
  Lines       36534    36533       -1     
==========================================
- Hits        33182    33167      -15     
- Misses       3352     3366      +14     

Impacted Files	Coverage Δ
src/bgw/scheduler.c	83.04% <0.00%> (-3.51%)	⬇️
src/bgw/job.c	91.97% <0.00%> (-0.34%)	⬇️
tsl/src/nodes/data_node_dispatch.c	97.10% <0.00%> (-0.25%)	⬇️
tsl/src/bgw_policy/job.c	96.85% <0.00%> (-0.01%)	⬇️

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[svenklemm]

I do not think your change will do anything. Most often the error is about the template database being accessed.
See: https://github.com/timescale/timescaledb/runs/3789743484?check_suite_focus=true for an example of a failed run

[fabriziomello]

I do not think your change will do anything. Most often the error is about the template database being accessed. See: https://github.com/timescale/timescaledb/runs/3789743484?check_suite_focus=true for an example of a failed run

You're correct, the error I'm getting time to time is the following:

diff -u /Users/runner/work/timescaledb/timescaledb/test/expected/pg_dump.out /Users/runner/work/timescaledb/timescaledb/build/test/results/pg_dump.out
--- /Users/runner/work/timescaledb/timescaledb/test/expected/pg_dump.out	2021-10-04 12:34:50.000000000 +0000
+++ /Users/runner/work/timescaledb/timescaledb/build/test/results/pg_dump.out	2021-10-04 12:45:01.000000000 +0000
@@ -601,14 +601,4 @@
 (0 rows)
 
 CREATE DATABASE db_dump_error WITH TEMPLATE :TEST_DBNAME;
---now test functions for permission errors
-\c  db_dump_error :ROLE_DEFAULT_PERM_USER_2
-\set ON_ERROR_STOP 0
-SELECT timescaledb_pre_restore();
-ERROR:  must be owner of database db_dump_error
-SELECT timescaledb_post_restore();
-ERROR:  must be owner of database db_dump_error
-\set ON_ERROR_STOP 1
---drop db
-\c :TEST_DBNAME :ROLE_SUPERUSER
-DROP DATABASE db_dump_error;
+ERROR:  source database "db_pg_dump" is being accessed by other users

Is db_pg_dump the template database you're talking about?