Fix error message when a hostaddr cannot be parsed.
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 7b02ba62e9).

Report and fix by Robert Haas.

Discussion: c52634642d263b0725d7a005afe274e44e4ded0b@mail.gmail.com

xinzweb/gpdb,greenplum-db/gpdb,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,greenplum-db/gpdb,adam8157/gpdb,50wu/gpdb,adam8157/gpdb,greenplum-db/gpdb,adam8157/gpdb,50wu/gpdb,50wu/gpdb,xinzweb/gpdb,adam8157/gpdb,lisakowen/gpdb,50wu/gpdb,xinzweb/gpdb,greenplum-db/gpdb,xinzweb/gpdb,adam8157/gpdb,adam8157/gpdb,xinzweb/gpdb,lisakowen/gpdb,50wu/gpdb,lisakowen/gpdb,lisakowen/gpdb,xinzweb/gpdb,50wu/gpdb,greenplum-db/gpdb,greenplum-db/gpdb,lisakowen/gpdb,xinzweb/gpdb,adam8157/gpdb,adam8157/gpdb,lisakowen/gpdb,greenplum-db/gpdb,50wu/gpdb,greenplum-db/gpdb,50wu/gpdb