Fix error message for Redis 3.2.3

Author: xplicit

tests/ServiceStack.Redis.Tests/RedisClientTests.cs

@@ -260,7 +260,8 @@ public void Can_BgSave()
             catch (RedisResponseException e)
             {
                 // if exception has that message then it still proves that BgSave works as expected.
-                if (e.Message.StartsWith("Can't BGSAVE while AOF log rewriting is in progress"))
+                if (e.Message.StartsWith("Can't BGSAVE while AOF log rewriting is in progress")
+                    || e.Message.StartsWith("An AOF log rewriting in progress: can't BGSAVE right now"))
                     return;
 
                 throw;