add option to set worker polling interval

[ilouzl]

A useful option to override the default 5 sec polling interval of the agent

[jkhenning]

Hi @ilouzl, looks good - can we add a minimum of 5 seconds? (less than that will just harass the server, I think)

[ilouzl]

Hi @jkhenning.
Sure!
Done

[ilouzl]

Hi @jkhenning I'm afraid the PR was buggy.
The deletion of _polling_interval = 5.0 will break services mode.
This is because Worker class now doesn't have a polling_interval member which will cause an error if invoked with commands other than daemon (such as clearml-agent execute in sevices mode).
Do you want me to start another PR for this?

[jkhenning]

Hi @ilouzl, yes, I see what you mean. I'll push a fix, thanks