Remove remote_exists function and add allow_failure=True

Fixes #15436

Get the `2014.7` branch inline with the `develop` branch and fix the salt-cloud regression on `develop`.
Merge pull request #15446 from terminalmage/gitfs-docs-corrections

More gitfs docs corrections/clarifications
Merge pull request #15443 from rallytime/fix_salt_cloud

Remove remote_exists function and add allow_failure=True
remove extraneous wording