Changes

setupcon: use /run for tempfiles

(and dump the various unnecessary fallback paths), since /run is always
mountable rw at least as early as /tmp is and is guaranteed to be
safe from tmpcleaners at boot.  Only keep /tmp as a fallback in case
we have access to write to /tmp and to a console, but not to /run.
LP: #1824227. Closes: Bug#1072204.