Created a new variable to allow execute set_permissions automatically

[mgallego]

This is a proposal of change, if finally accepted I'll change the necessary documentation.

I Created a new param use_set_permissions false by default, to set if want to execute the set_permissions task automatically.

If the variable is set to true execute set_permissions running the validators of the task (checking the existence of the necessary variables)

[willdurand]

Makes sense, thank you!