BUG #15888: Bogus "idle in transaction" state for logical decoding client after creating a slot

The following bug has been logged on the website:

Bug reference: 15888
Logged by: Marko Tiikkaja
Email address: marko(at)joh(dot)to
PostgreSQL version: 9.6.14
Operating system: OS X 10.12.6
Description:

Run:

pg_recvlogical -S foo -f /dev/null -d dbname --create-slot --start

and pg_stat_activity will show something like this until that session
disconnects:

-[ RECORD 1
]----+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
datid | 9672230
datname | dbname
pid | 81996
usesysid | 10
usename | marko
application_name | pg_recvlogical
client_addr |
client_hostname |
client_port | -1
backend_start | 2019-07-03 10:02:00.459737+02
xact_start |
query_start |
state_change | 2019-07-03 10:02:00.726645+02
wait_event_type |
wait_event |
state | idle in transaction
backend_xid |
backend_xmin |
query |

which is quite obviously bogus.