Speedup UnitOfWork#queue_name

Profiling with bin/sidekiqload, results:
1. cpu
Before:
```
      1046   (4.7%)        1046   (4.7%)     Sidekiq::BasicFetch::UnitOfWork#queue_name
```
After:
```
       331   (1.3%)         331   (1.3%)     Sidekiq::BasicFetch::UnitOfWork#queue_name
```

2. object allocations
Before:
```
    400012   (4.7%)      400012   (4.7%)     Sidekiq::BasicFetch::UnitOfWork#queue_name
```
After:
```
    100003   (1.2%)      100003   (1.2%)     Sidekiq::BasicFetch::UnitOfWork#queue_name
```

lib/sidekiq/fetch.rb

@@ -14,12 +14,12 @@ module Sidekiq
       end
 
       def queue_name
-        queue.sub(/.*queue:/, "")
+        queue.delete_prefix("queue:")
       end
 
       def requeue
         Sidekiq.redis do |conn|
-          conn.rpush("queue:#{queue_name}", job)
+          conn.rpush(queue, job)
         end
       end
     }
@@ -61,14 +61,14 @@ module Sidekiq
       Sidekiq.logger.debug { "Re-queueing terminated jobs" }
       jobs_to_requeue = {}
       inprogress.each do |unit_of_work|
-        jobs_to_requeue[unit_of_work.queue_name] ||= []
-        jobs_to_requeue[unit_of_work.queue_name] << unit_of_work.job
+        jobs_to_requeue[unit_of_work.queue] ||= []
+        jobs_to_requeue[unit_of_work.queue] << unit_of_work.job
       end
 
       Sidekiq.redis do |conn|
         conn.pipelined do
           jobs_to_requeue.each do |queue, jobs|
-            conn.rpush("queue:#{queue}", jobs)
+            conn.rpush(queue, jobs)
           end
         end
       end

test/test_fetch.rb

@@ -5,12 +5,18 @@ require 'sidekiq/api'
 
 describe Sidekiq::BasicFetch do
   before do
+    @prev_redis = Sidekiq.instance_variable_get(:@redis)
+    Sidekiq.redis = { :namespace => 'fuzzy' }
     Sidekiq.redis do |conn|
-      conn.flushdb
+      conn.redis.flushdb
       conn.rpush('queue:basic', 'msg')
     end
   end
 
+  after do
+    Sidekiq.redis = @prev_redis
+  end
+
   it 'retrieves' do
     fetch = Sidekiq::BasicFetch.new(:queues => ['basic', 'bar'])
     uow = fetch.retrieve_work
@@ -31,12 +37,22 @@ describe Sidekiq::BasicFetch do
   end
 
   it 'bulk requeues' do
+    Sidekiq.redis do |conn|
+      conn.rpush('queue:foo', ['bob', 'bar'])
+      conn.rpush('queue:bar', 'widget')
+    end
+
     q1 = Sidekiq::Queue.new('foo')
     q2 = Sidekiq::Queue.new('bar')
+    assert_equal 2, q1.size
+    assert_equal 1, q2.size
+
+    fetch = Sidekiq::BasicFetch.new(:queues => ['foo', 'bar'])
+    works = 3.times.map { fetch.retrieve_work }
     assert_equal 0, q1.size
     assert_equal 0, q2.size
-    uow = Sidekiq::BasicFetch::UnitOfWork
-    Sidekiq::BasicFetch.bulk_requeue([uow.new('fuzzy:queue:foo', 'bob'), uow.new('fuzzy:queue:foo', 'bar'), uow.new('fuzzy:queue:bar', 'widget')], {:queues => []})
+
+    Sidekiq::BasicFetch.bulk_requeue(works, {:queues => []})
     assert_equal 2, q1.size
     assert_equal 1, q2.size
   end