pgsql: Fix bug per Oleksiy Shchukin - 2nd argument for

Log Message:
-----------
Fix bug per Oleksiy Shchukin - 2nd argument for dblink_get_result(text,bool)
is PG_GETARG_BOOL(2), should be PG_GETARG_BOOL(1).

Apply simple fix to back branches only. More extensive change to be applied
to head per Tom's suggestion.

Tags:
----
REL8_3_STABLE

Modified Files:
--------------
    pgsql/contrib/dblink:
        dblink.c (r1.69.2.1 -> r1.69.2.2)
        (http://anoncvs.postgresql.org/cvsweb.cgi/pgsql/contrib/dblink/dblink.c?r1=1.69.2.1&r2=1.69.2.2)