Add try catch when getting the sensor values

When the driver of the source sensors is binding, the sensor service name
is available but the value property can be unavailable in short time.
Getting the sensor value without try catch can cause exception "sd_bus_call: \
org.freedesktop.DBus.Error.ServiceUnknown: The name is not activatable".
This commit catchs the exception when getting sensor value to cover that case.

Signed-off-by: Thu Ba Nguyen <thu@os.amperecomputing.com>
Change-Id: If946f20e38020767d418d6d80caf4e74db7b49ab
1 file changed