disabling kernel messages (dmesg -n 1) is not realiable

After the login_prompt of "Please press Enter to activate this console.", the ShellDriver writes dmesg -n 1 on the console to disable kernel messages on the console. But this does not always work. Sometimes the first couple characters are missing, sometime random characters are missing. Here are some examples from the log...

CONSOLE SerialLogger.ma:     SerialDriver(main) > dmesg -n 1␤␍␤
INFO         StepLogger:     → SerialDriver.expect(pattern=['root@[-\\w()]+:[^ ]+ ', 'Please press Enter to activate this console.', 'Password: ', <class 'pexpect.exceptions.TIMEOUT'>]) 
CONSOLE SerialLogger.ma:      SerialDriver(main) < mesg -n 1␍␤
CONSOLE SerialLogger.ma:      SerialDriver(main) < -ash: mesg: not found␍␤

INFO         StepLogger:     → SerialDriver.expect(pattern=['root@[-\\w()]+:[^ ]+ ', 'Please press Enter to activate this console.', 'Password: ', <class 'pexpect.exceptions.TIMEOUT'>]) 
CONSOLE SerialLogger.ma:      SerialDriver(main) < ms- ␍␤
CONSOLE SerialLogger.ma:      SerialDriver(main) < -ash: ms-: not found␍␤

Perhaps some kind of check to see if dmesg -n 1 worked would be useful, which can be done by checking the contents of /proc/sys/kernel/printk. Or possibly it would be beneficial to add a sleep (user configurable with a default of 0 seconds) before running dmesg -n 1.

Start with the ShellDriver handling after the login_prompt and reproduce the serial-console examples where dmesg -n 1 is truncated. Compare the command result with /proc/sys/kernel/printk, then define done as reliably disabling kernel messages, with any delay configurable if that approach is chosen.