GRANT rights to CURRENT_USER instead of adding roles

We shouldn't be adding roles during the regression tests as that can
cause back-to-back installcheck runs to fail and users running the
regression tests likley don't want those extra roles.

Pointed out by Tom

src/test/regress/expected/init_privs.out

@@ -6,8 +6,7 @@ SELECT count(*) > 0 FROM pg_init_privs;
  t
 (1 row)
 
-CREATE ROLE init_privs_test_role1;
-CREATE ROLE init_privs_test_role2;
 -- Intentionally include some non-initial privs for pg_dump to dump out
-GRANT SELECT ON pg_proc TO init_privs_test_role1;
-GRANT SELECT (prosrc) ON pg_proc TO init_privs_test_role2;
+GRANT SELECT ON pg_proc TO CURRENT_USER;
+GRANT SELECT (prosrc) ON pg_proc TO CURRENT_USER;
+GRANT SELECT (rolname, rolsuper) ON pg_authid TO CURRENT_USER;

src/test/regress/sql/init_privs.sql

@@ -3,9 +3,8 @@
 -- There should always be some initial privileges, set up by initdb
 SELECT count(*) > 0 FROM pg_init_privs;
 
-CREATE ROLE init_privs_test_role1;
-CREATE ROLE init_privs_test_role2;
-
 -- Intentionally include some non-initial privs for pg_dump to dump out
-GRANT SELECT ON pg_proc TO init_privs_test_role1;
-GRANT SELECT (prosrc) ON pg_proc TO init_privs_test_role2;
+GRANT SELECT ON pg_proc TO CURRENT_USER;
+GRANT SELECT (prosrc) ON pg_proc TO CURRENT_USER;
+
+GRANT SELECT (rolname, rolsuper) ON pg_authid TO CURRENT_USER;