make-secnet-sites: Tainted: Fix a lot of bad return values

make-secnet-sites: Tainted: Fix a lot of bad return values

This code had remnants of a previously intended calling convention,
where object return chaining would be used.

Unfortunately in the currently used calling style, we expect to get a
boolean back everywhere, where true meas `ok'.  Returning `self' is
always treated as `ok' because it's trueish.

Luckily this doesn't cause actual security bugs because we always
return from all of the top-level entrypoints via ._rtn[val] which
checks the ._ok setting, which does properly track problems.  So we
fail an assertion rather than printing a nice message.  This is not
pretty but it is not a vulnerability.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>