Log external detection as busy status (#385)

Log external detection as busy status (#385)

* Log external detection as busy status

This message is generally not wanted in the final output, since it's used only
to signal alr is not dead/stuck, but busy. Also, it must be entirely removed
from some commands like `alr setenv` or the output is no longer parseable.

* Detect output redirection to adjust logging

* Switch --no-tty to disable control chars in output

* Fix tests for the changed output