allow disabling module invocation logging

Add a new option "disable_invocation_logging" to the ansible.cfg
configuration that allows disabling the syslog logging of remote
module invocations.

This addresses bug #5525 - feedback very welcome.

One implementation question - it appears that the AnsibleModule.__init__(... no_log ...) parameter is not used and can be removed (checked via git grep). Of course for the paramters no_log is used and I won't touch that. If that sounds reasonable I will remove it. If its part of a exported API for 3rd party module I obviously will not change anything here.

Thanks for your consideration,
 Michael