fix fifottl_fiber_iteration error handling

fifottl_fiber pcalls fifottl_fiber_iteration and then handles
result. Returned error code comparison with box.error.READONLY
was not done properly. Now it is fixed. Corresponding test case:
buried task in dropped queue scenario is added.

Closes #96

Author: PersDep

queue/abstract/driver/fifottl.lua

@@ -164,7 +164,7 @@ local function fifottl_fiber(self)
     while true do
         if not box.cfg.read_only then
             local stat, err = pcall(fifottl_fiber_iteration, self, processed)
-            if not stat and not err.code == box.error.READONLY then
+            if not stat and not (err.code == box.error.READONLY) then
                 log.error("error catched: %s", tostring(err))
                 log.error("exiting fiber '%s'", fiber.name())
                 return 1

t/020-fifottl.t

@@ -2,7 +2,7 @@
 local fiber = require('fiber')
 
 local test = require('tap').test()
-test:plan(14)
+test:plan(15)
 
 local queue = require('queue')
 local state = require('queue.abstract.state')
@@ -245,6 +245,23 @@ test:test('ttl after delay test', function(test)
     test:is(task.ttr, TTR * 1000000, 'check TTR after release')
 end)
 
+-- gh-96: infinite loop after dropping a tube with a burried task
+test:test('buried task in a dropped queue', function(test)
+    test:plan(1)
+
+    local TASK_ID = 1
+    local tube = queue.create_tube('test_drop_with_burried', 'fifottl',
+        {ttr = 0.1, if_not_exist = true})
+
+    tube:put({foo = 'bar'})
+    local task = tube:take(0)
+    tube:bury(task[TASK_ID])
+
+    tube:drop()
+    fiber.sleep(0.2)
+    test:ok(true, 'queue does not hang')
+end)
+
 
 tnt.finish()
 os.exit(test:check() == true and 0 or -1)