Way, way backwards compatibility for beanstalk-export.rb

I had to do an export from a really old version of beanstalkd that
didn't support reserve-with-timeout.  This works, but it's not very
efficient.  The code will try to do the most efficient thing and
fallback on less efficient/more dumb things as it needs to.

bin/beanstalk-export.rb

@@ -14,7 +14,15 @@ def kick(n=10000000)
 
 def export(t)
   loop do
-    job = BS.reserve 0
+    job = begin
+      BS.reserve 0
+    rescue Beanstalk::BadFormatError
+      # Hacky way to handle a really old version.
+      st = BS.stats_tube t
+      remaining = st['current-jobs-urgent'] + st['current-jobs-ready']
+      raise Beanstalk::TimedOut if remaining == 0
+      BS.reserve
+    end
 
     # Record the time the job should actually start.
     d = Time.now.to_i + job.delay