switchroot: Don't log if running as pid1, minor code style cleanups

switchroot: Don't log if running as pid1, minor code style cleanups

If we're running as pid1, avoid printing anything in the normal
success paths as we don't want to affect the physical console by
default; the device may be using a splash screen, etc.

Also cleanup the code a bit to use a single variable
`running_as_pid1`, declare-and-initialize, use the
`bool` type, etc.

Closes: #1531
Approved by: jlebon