job submit fails if memcached restarted

[p-alik]

To reproduse:

• start gearmand
  gearmand --verbose DEBUG -p 4731 --queue-type libmemcached --libmemcached-servers 127.0.0.1:11211
• restart mamcached
• try to submit a job

  DEBUG 2017-04-04 10:21:02.105022 [  main ] accept() fd:33 -> libgearman-server/gearmand.cc:874
   INFO 2017-04-04 10:21:02.105048 [  main ] Accepted connection from 127.0.0.1:34995
  DEBUG 2017-04-04 10:21:02.105084 [     2 ] Received CON wakeup event -> libgearman-server/gearmand_thread.cc:619
  DEBUG 2017-04-04 10:21:02.105105 [     2 ]       127.0.0.1:34995 Watching  POLLIN  -> libgearman-server/gearmand_thread.cc:151
  DEBUG 2017-04-04 10:21:02.105115 [     2 ] Gear connection made: 127.0.0.1:34995 -> libgearman-server/plugins/protocol/gear/protocol.cc:407
  DEBUG 2017-04-04 10:21:02.107196 [     2 ] 127.0.0.1:34995 Ready     POLLIN  -> libgearman-server/gearmand_con.cc:138
  DEBUG 2017-04-04 10:21:02.107219 [     2 ] read 56 bytes -> libgearman-server/io.cc:798
  DEBUG 2017-04-04 10:21:02.107227 [     2 ] Gear unpack -> libgearman-server/plugins/protocol/gear/protocol.cc:117
  DEBUG 2017-04-04 10:21:02.107236 [     2 ] GEAR SUBMIT_JOB_BG -> libgearman-server/plugins/protocol/gear/protocol.cc:285
  DEBUG 2017-04-04 10:21:02.107244 [     2 ] Received GEARMAN_SUBMIT_JOB_BG -> libgearman-server/thread.cc:311
  DEBUG 2017-04-04 10:21:02.107256 [     2 ]       127.0.0.1:34995 Watching  POLLIN  -> libgearman-server/gearmand_thread.cc:151
  DEBUG 2017-04-04 10:21:02.107278 [  proc ] PACKET COMMAND: GEARMAN_SUBMIT_JOB_BG -> libgearman-server/server.cc:119
  DEBUG 2017-04-04 10:21:02.107290 [  proc ] Received submission, function:foo unique:decb94cf-3a6f-4a57-8e69-bfb27a2cf845 with 2 arguments -> libgearman-server/server.cc:248
  DEBUG 2017-04-04 10:21:02.107300 [  proc ] Comparing queue 2 to limit 0 for priority 1 -> libgearman-server/job.cc:175
  DEBUG 2017-04-04 10:21:02.107309 [  proc ] JOB H:batch0-01.lab.ip-platform.net:6 :2280373038 -> libgearman-server/job.cc:240
  DEBUG 2017-04-04 10:21:02.107316 [  proc ] SHUTDOWN VALUE false -> libgearman-server/plugins/base.cc:97
  DEBUG 2017-04-04 10:21:02.107324 [  proc ] libmemcached add: decb94cf-3a6f-4a57-8e69-bfb27a2cf845 -> libgearman-server/plugins/queue/libmemcached/queue.cc:201
  ERROR 2017-04-04 10:21:02.107391 [  proc ] (140386107796272) CONNECTION FAILURE, ::rec() returned zero, server has disconnected, host: 127.0.0.1:11211 -> libmemcached/io.cc:456 add(QUEUE_ERROR) -> libgearman-server/plugins/queue/libmemcached/queue.cc:215
  ERROR 2017-04-04 10:21:02.107404 [  proc ] gearman_server_job_add gearman_server_run_command(QUEUE_ERROR) -> libgearman-server/server.cc:301
WARNING 2017-04-04 10:21:02.107412 [  proc ] GEARMAN_QUEUE_ERROR:QUEUE_ERROR -> libgearman-server/server.cc:302
  DEBUG 2017-04-04 10:21:02.107499 [     2 ] Received RUN wakeup event -> libgearman-server/gearmand_thread.cc:624
  DEBUG 2017-04-04 10:21:02.107512 [     2 ] GEAR ERROR -> libgearman-server/plugins/protocol/gear/protocol.cc:318
  DEBUG 2017-04-04 10:21:02.107530 [     2 ] send() 35 bytes to peer -> libgearman-server/io.cc:403
  DEBUG 2017-04-04 10:21:02.107538 [     2 ] Sent ERROR -> libgearman-server/thread.cc:356
  DEBUG 2017-04-04 10:21:02.107884 [     2 ] 127.0.0.1:34995 Ready     POLLIN  -> libgearman-server/gearmand_con.cc:138
   INFO 2017-04-04 10:21:02.107901 [     2 ] Peer connection has called close()
   INFO 2017-04-04 10:21:02.107909 [     2 ] Disconnected 127.0.0.1:34995
  DEBUG 2017-04-04 10:21:02.107996 [     2 ] Received RUN wakeup event -> libgearman-server/gearmand_thread.cc:624
   INFO 2017-04-04 10:21:02.108009 [     2 ] Gear connection disconnected: -:-