loop: Free the parent queue last when destroying the loop

This avoids a heap-use-after-free ASAN error. Close #3334

test/functional/ex_cmds/quit_spec.lua

@@ -0,0 +1,14 @@
+local helpers = require('test.functional.helpers')
+local execute, eq, clear = helpers.execute, helpers.eq, helpers.clear
+
+describe(':qa', function()
+  before_each(function() 
+    clear('qa')
+  end)
+
+  it('verify #3334', function()
+    -- just testing if 'qa' passed as a program argument wont result in memory
+    -- errors
+  end)
+end)
+