passenger-status shows passenger workers hanging

Issue

• We have 8 passenger-work threads in hung state (i.e. not processing any requests):

# passenger-status
Version : 4.0.18
Date    : 2018-06-04 17:03:37 +0200
Instance: 11963
----------- General information -----------
Max pool size : 24
Processes     : 24
Requests in top-level queue : 0

----------- Application groups -----------
/usr/share/foreman#default:
  App root: /usr/share/foreman
  Requests in queue: 192
  * PID: 30131   Sessions: 1       Processed: 991     Uptime: 2h 9m 8s
    CPU: 3%      Memory  : 562M    Last used: 1h 53m 51s
  * PID: 32450   Sessions: 1       Processed: 966     Uptime: 2h 8m 15s
    CPU: 4%      Memory  : 463M    Last used: 1h 48m 17
  * PID: 4693    Sessions: 1       Processed: 939     Uptime: 2h 6m 32s
    CPU: 3%      Memory  : 470M    Last used: 1h 50m 48
  * PID: 17452   Sessions: 1       Processed: 987     Uptime: 2h 1m 33s
    CPU: 4%      Memory  : 601M    Last used: 1h 41m 3s
  * PID: 15738   Sessions: 1       Processed: 993     Uptime: 1h 50m 33s
    CPU: 4%      Memory  : 590M    Last used: 1h 34m 5
  * PID: 21930   Sessions: 1       Processed: 380     Uptime: 1h 33m 34s
    CPU: 1%      Memory  : 528M    Last used: 1h 29m 4
  * PID: 26190   Sessions: 1       Processed: 544     Uptime: 1h 31m 34s
    CPU: 2%      Memory  : 490M    Last used: 1h 23m 5
  * PID: 32380   Sessions: 1       Processed: 36      Uptime: 1h 0m 29s
    CPU: 0%      Memory  : 561M    Last used: 1h 0m 3s

• qpid has died.