LP #1719506: Audit plugin reports "command_class=error" for server-side prepared statements

**Reported in Launchpad by Andrew Garner last update 05-10-2017 03:12:43

When logging a prepared statement through the prepared statement api, the command class is logged as "error" even for successful executions.

Here is an example snippet from logs where a successful "SHOW GLOBAL VARIABLES WHERE Variable_name = ?", "max_allowed_packet" is executed:

{"audit_record":{"name":"Prepare","record":"132355_2017-09-26T04:31:44","timestamp":"2017-09-26T04:31:57 UTC","command_class":"error","connection_id":"4","status":0,"sqltext":"","user":"root[root] @ [127.0.0.1]","host":"","os_user":"","ip":"127.0.0.1","db":""}}
{"audit_record":{"name":"Execute","record":"132356_2017-09-26T04:31:44","timestamp":"2017-09-26T04:31:57 UTC","command_class":"error","connection_id":"4","status":0,"sqltext":"SHOW GLOBAL VARIABLES WHERE Variable_name = 'max_allowed_packet'","user":"root[root] @ [127.0.0.1]","host":"","os_user":"","ip":"127.0.0.1","db":""}}
{"audit_record":{"name":"Close stmt","record":"132357_2017-09-26T04:31:44","timestamp":"2017-09-26T04:31:57 UTC","command_class":"error","connection_id":"4","status":0,"sqltext":"","user":"root[root] @ [127.0.0.1]","host":"","os_user":"","ip":"127.0.0.1","db":""}}

This seems to be due to the audit api setting general_sql_command based on sql_statement_names, where there's no matching entry for the current binary protocol command.

This is confusing for users consuming these logs who might be using server-side prepared statements.