cannot drop replication slot if server is running in single-user mode

Hi,

I found that if server is running in single-user mode , there we can 
create replication slot but cannot drop it .

backend> SELECT * FROM pg_create_physical_replication_slot('p');
2018-03-06 13:20:03.441 GMT [14869] LOG:  statement: SELECT * FROM 
pg_create_physical_replication_slot('p');

      1: slot_name    (typeid = 19, len = 64, typmod = -1, byval = f)
      2: lsn    (typeid = 3220, len = 8, typmod = -1, byval = t)
     ----
      1: slot_name = "p"    (typeid = 19, len = 64, typmod = -1, byval = f)
     ----
backend> select pg_drop_replication_slot('p');
2018-03-06 13:20:24.390 GMT [14869] LOG:  statement: select 
pg_drop_replication_slot('p');

      1: pg_drop_replication_slot    (typeid = 2278, len = 4, typmod = 
-1, byval = t)
     ----
2018-03-06 13:20:24.391 GMT [14869] ERROR:  epoll_ctl() failed: Bad file 
descriptor
2018-03-06 13:20:24.391 GMT [14869] STATEMENT:  select 
pg_drop_replication_slot('p');

-- 
regards,tushar
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