burn: Delete known_hosts file in case of reburn (edit documentation)

[dkkolli]

• add to the FAQ in the tutorial.

[laszewsk]

should go in FAQ at the end

[laszewsk]

there is a shell command that does this actually, we need to look this up and create a Shell.delete_knowhosts or somewhere else convenient. para,eteri is a string or a list
if type(parameter) == str:
parameter = [parameter]

now everything is a list and we can do list based function