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@joh.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.