citus_lock_waits intermittently fails with epoll_ctl() failed: No such file or directory

citus head as of dec 5 ( 9c254859bff89026718187d4b208de4a6e8fba3a )

```
citus=> select * from citus_lock_waits limit 139; \watch 0.01
(0 rows)

Time: 89.115 ms
(0 rows)

Time: 89.402 ms
(0 rows)

Time: 88.678 ms
(0 rows)

Time: 88.883 ms
(0 rows)

Time: 89.457 ms
(0 rows)

Time: 90.791 ms
(0 rows)

Time: 89.169 ms
(0 rows)

Time: 92.670 ms
(0 rows)

Time: 91.503 ms
(0 rows)

Time: 90.442 ms
ERROR: epoll_ctl() failed: No such file or directory
```