[Elastic Agent] Remove prompt on first enrollment

[mostlyjason]

Currently when you install Elastic Agent for the first time and then issue the enroll command it prompts the user "This will replace your current settings. Do you want to continue? [Y/n]" However, there are no current settings so it should not show this prompt. It should only be shown when overwriting existing settings. Additionally, let's confirm it can be disabled with the -f flag which will default to overwriting the settings.

[mostlyjason]

Just tested the -f flag and it worked