Fix a problem introduced with #1101 and optimize privilege handling

* If a db user belonged to a role which had a privilege, the user would
  not have the privilege added as the role gave the appearance that the
  user already had it.  Fixed to always check the privileges specific to
  the user.
* Make fewer db queries to determine if privileges need to be changed
  and change them (was four for each privilege.  Now two for each object
  that has a set of privileges changed).

lib/ansible/modules/database/postgresql/postgresql_user.py

@@ -419,8 +419,6 @@ def revoke_privileges(cursor, user, privs):
         return False
 
     changed = False
-    revoke_funcs = dict(table=revoke_table_privilege, database=revoke_database_privilege)
-    check_funcs = dict(table=has_table_privilege, database=has_database_privilege)
     for type_ in privs:
         revoke_func = {
             'table':revoke_table_privilege,
@@ -436,8 +434,9 @@ def revoke_privileges(cursor, user, privs):
 def grant_privileges(cursor, user, privs):
     if privs is None:
         return False
-    grant_funcs = dict(table=grant_table_privilege, database=grant_database_privilege)
-    check_funcs = dict(table=has_table_privilege, database=has_database_privilege)
+
+    grant_funcs = dict(table=grant_table_privileges, database=grant_database_privileges)
+    check_funcs = dict(table=has_table_privileges, database=has_database_privileges)
 
     changed = False
     for type_ in privs: