Improve logic from main install to post install

[aarz-snl]

Right now if you run post install too early users can run into various issues when running the post install playbook.

Recommendation is to wait 4-5 minutes for all services to be up -- including the Fleet Agent before running post install.

This should automated better during install. One suggestion would be to move fleet agent service install and startup to the post install playbook. This service should be started up after fleet settings have been applied to avoid any issues.