[v4] Default to avoiding syncing .treeinfo

[dralley]

Is your feature request related to a problem? Please describe.
Treeinfo doesn't really belong in the same category as the other skip_types. It's a different type of thing.

Most users don't need them at all, only ones who require PXE booting support.

Describe the solution you'd like

There should be a toggleable option on the remote which determines whether or not to sync distributions trees / subrepos.

[dralley]

Re-evaluate how we handle .treeinfo that is not a properly well-formatted INI, e.g. HTML pages that say 404

[ggainey]

2 issues here - 1) treeinfo shouldn't be lumped into skip_types, because it's really not an RPM-metadata-type, and 2) 'sync treeinfo' should default to False, not True - most users don't actually want/need them even they do exist.