Add option to disable rrd locking during cgi calls

[bachandi]

For modules that need to call the cgi function internally an option to disable the locking would be nice. This way the update function can call the cgi function to produce plots from reports for example.

[mikaku]

Do you have a real use case for this?
Not that I'm contrary to it, just want to know why not using the global config for that.

[bachandi]

For modules that produce some reports and need to run cgi method to produce the plots this is needed if the config specifies rrd_locking. This way it is possible to call the cgi method inside the update from time to time.

[mikaku]

Thanks.