test: add workaround for gh_3211_per_module_log_level_test

Periodically this test hangs on pthread_join() on macOS.
This patch adds a workaround until #8423 is implemented.

Closes #8420

NO_DOC=test fix
NO_CHANGELOG=test fix

(cherry picked from commit f1ae7264)

test/box-luatest/gh_3211_per_module_log_level_test.lua

@@ -42,12 +42,16 @@ g2.before_each(function(cg)
     end, {cg.params.cfg_type})
 end)
 
-g1.after_each(function(cg)
+local function drop_server(cg)
+    -- TODO(gh-8423): Remove this workaround.
+    -- If log level is 'debug' during server:drop(), the test may hang on macOS
+    -- (see gh-8420).
+    cg.server:update_box_cfg({log_level = 'info',
+                             log_modules = {tarantool = 'info'}})
     cg.server:drop()
-end)
-g2.after_each(function(cg)
-    cg.server:drop()
-end)
+end
+g1.after_each(drop_server)
+g2.after_each(drop_server)
 
 -- Test log.new{...}
 g1.test_log_new = function(cg)