lsof -F broken in Xenial

[Gustavo Niemeyer]

The -F option of lsof informs the tool the output format.

For some reason the release in Xenial changed the output format so that now "f" is always part of the output.

Even despite the obvious breakage that can occur with this change (that's how I found it), it's really hard to understand the background for such a change.

The -F option defines the output format. If the user wants "f" to be generated, just have "f" in the requested format, as it always worked and seems most obvious.