Allow disabling existing repositories to install Salt

[doesitblend]

Description of Issue/Question

Testing the bootstrap script with Saltify recently I wasn't able to use either the -r or -R options to ignore existing repository configurations for CentOS 7. The custom script I am using is just a downloaded copy of the bootstrap script with salt-cloud -u and then renamed to test using the custom script argument.

Setup

Please see the attached Saltify configuration for usage.

saltify.tar.gz

Steps to Reproduce Issue

Have a saltstack repository already configured and point it to a random URL, or update the configuration here to point to a random host.

Then execute with the following:

# salt-cloud -m /etc/salt/cloud.maps.d/hyperv.conf -P

Versions and Systems

(salt --versions-report, bootstrap-salt.sh -v, system type and version, cloud/VM provider as appropriate.)