BUG #16508: using multi-host connection string when the first host is starting fails

The following bug has been logged on the website:

Bug reference:      16508
Logged by:          Cyril Jouve
Email address:      jv.cyril@gmail.com
PostgreSQL version: 10.11
Operating system:   rhel7
Description:

Hello,

I'm connection to pg10 using psql (tried with clients psql 10.11 & psql
12.2) using a connection string such as:
psql 'dbname=xxxxx1,xxxxx2,xxxxx3,xxxxx4 target_session_attrs=read-write'

the connection to first database (xxxxx1) fail with the error:
psql.bin: FATAL:  the database system is starting up

which is correct according to postgres state on that machine,
but then I would expect the psql tries the next server (xxxxx2) with is in
the one acceptiong the connection params (target_session_attrs=read-write)

instead of the error.

If I swap the connection parameters like this: psql
'dbname=xxxxx2,xxxxx1,xxxxx3,xxxxx4 target_session_attrs=read-write'
(swapped xxxx1/xxxx2), psql is able to connect to xxxxx2.