do not add mf2 to default comment author avatar

[sknebel]

Right now it seems that if a comment author has no avatar, the displayed default image is still marked up as u-photo. This shouldn't happen. (Observed this on jgmac1106's site, which is running the indieweb-2016 theme, in case the theme is relevant for this)

[dshanske]

This should now be doable now that we are hosting the default locally instead of WordPress serving even the anonymous avatars through Gravatar

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.