Fix error message when a hostaddr cannot be parsed.

We were incorrectly passing hostname, not hostaddr, in the error message,
and because of that, you got:

$ psql 'hostaddr=foo'
psql: could not parse network address "(null)": Name or service not known

Backpatch to v10, where this was broken (by commit 7b02ba62).

Report and fix by Robert Haas.

Discussion: https://www.postgresql.org/message-id/CA+TgmoapFQA30NomGKEaZCu3iN7mF7fux8fbbk9SouVOT2JP7w@mail.gmail.com

src/interfaces/libpq/fe-connect.c

@@ -1751,7 +1751,7 @@ connectDBStart(PGconn *conn)
 				if (ret || !ch->addrlist)
 					appendPQExpBuffer(&conn->errorMessage,
 									  libpq_gettext("could not parse network address \"%s\": %s\n"),
-									  ch->host, gai_strerror(ret));
+									  ch->hostaddr, gai_strerror(ret));
 				break;
 
 			case CHT_UNIX_SOCKET: