altoslib: Disable telemetry while getting config data

We're seeing some log files created without a suitable -via- number
included. My hypothesis is that incoming telemetry is getting
interleaved with the configuration data containing the serial
number. This change simply disables telemetry while retrieving the
configuration data to try and keep that from happening.

Signed-off-by: Keith Packard <keithp@keithp.com>