darwin: downgrade error message on failure to open interface to info

darwin: downgrade error message on failure to open interface to info

This resolves an issue introduced by the implementation of the kernel detach code. This
code used claim_interface to detect if a kernel driver is attached. The issue is that if
a driver is attached or the interface is not available and an error message was printed
out. Since this is not an error the info level is more appropriate.

Also downgrading a number of warnings to clean up the output.

Closes #955

Signed-off-by: Nathan Hjelm <hjelmn@google.com>