Give a better error message on invalid hostaddr option.

Give a better error message on invalid hostaddr option.

If you accidentally pass a host name in the hostaddr option, e.g.
hostaddr=localhost, you get an error like:

psql: could not translate host name "localhost" to address: Name or service not known

That's a bit confusing, because it implies that we tried to look up
"localhost" in DNS, but it failed. To make it more clear that we tried to
parse "localhost" as a numeric network address, change the message to:

psql: could not parse network address "localhost": Name or service not known

Discussion: https://www.postgresql.org/message-id/10badbc6-4d5a-a769-623a-f7ada43e14dd@iki.fi