units: bring agetty command lines back into sync

units: bring agetty command lines back into sync

Let's always rely on our own TTY reset logic and tty disallocation/clear
screen logic, thus always pass --noclear and --noreset.

Also, bring the list of baud rates to try into sync for console-getty
and serial-getty (the former might or might not be connected to rs232,
we can't know, hence assume the worst, and copy what
serial-getty@.service does)