test: fix box/misc failure in parallel mode

Rewrite the test so that it doesn't depend on timeouts, which can be
exceeded under high load, and simplify it a little.

Closes #4134

test/box/misc.result

@@ -1378,16 +1378,17 @@ _ = box.ctl.on_shutdown(function() print("on_shutdown 5") end)
 ...
 -- Check that we don't hang infinitely after os.exit()
 -- even if the following code doesn't yield.
-fiber = require("fiber")
----
-...
-_ = fiber.create(function() fiber.sleep(0.05) os.exit() while true do end end)
+fiber = require('fiber')
 ---
 ...
 test_run:cmd("switch default")
 ---
 - true
 ...
+test_run:eval("test", "_ = fiber.new(function() os.exit() while true do end end)")
+---
+- []
+...
 fiber.sleep(0.1)
 ---
 ...
@@ -1401,11 +1402,7 @@ test_run:cmd("start server test")
 ---
 - true
 ...
-test_run:cmd("switch test")
----
-- true
-...
-test_run:grep_log('test', 'on_shutdown 5', nil, {noreset=true})
+test_run:wait_log('test', 'on_shutdown 5', nil, 5, {noreset=true})
 ---
 - on_shutdown 5
 ...
@@ -1414,10 +1411,6 @@ test_run:grep_log('test', 'signal', nil, {noreset=true})
 ---
 - null
 ...
-test_run:cmd("switch default")
----
-- true
-...
 test_run:cmd("stop server test")
 ---
 - true

test/box/misc.test.lua

@@ -398,19 +398,17 @@ test_run:cmd("switch test")
 _ = box.ctl.on_shutdown(function() print("on_shutdown 5") end)
 -- Check that we don't hang infinitely after os.exit()
 -- even if the following code doesn't yield.
-fiber = require("fiber")
-_ = fiber.create(function() fiber.sleep(0.05) os.exit() while true do end end)
+fiber = require('fiber')
 test_run:cmd("switch default")
+test_run:eval("test", "_ = fiber.new(function() os.exit() while true do end end)")
 fiber.sleep(0.1)
 -- The server should be already stopped by os.exit(),
 -- but start doesn't work without a prior call to stop.
 test_run:cmd("stop server test")
 test_run:cmd("start server test")
-test_run:cmd("switch test")
-test_run:grep_log('test', 'on_shutdown 5', nil, {noreset=true})
+test_run:wait_log('test', 'on_shutdown 5', nil, 5, {noreset=true})
 -- make sure we exited because of os.exit(), not a signal.
 test_run:grep_log('test', 'signal', nil, {noreset=true})
-test_run:cmd("switch default")
 test_run:cmd("stop server test")
 test_run:cmd("cleanup server test")
 test_run:cmd("delete server test")