cli: Log fully quoted command line

Instead of logging the concatenated arguments, with this patch every
command will properly quote its full command line. This makes it easier
to just copy-and-paste commands from “commands.log” to re-run them. Also
remove a case of “x = a or b” for non-boolean values.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>