Client_python crash when generating Hadoop metrics

[minh tien]

I used https://github.com/opsnull/hadoop_jmx_exporter library to generate prometheus metrics for hadoop cluster. Alter i run the  exporter, it raise a format error in function generate_latest (exposition.py).

The root cause is hadoop_jmx_exporter which send invalid input to this function (ex: line.value = "DISK")  and make floatToGoString function to fail.

I know it's client error but i think it's better to return negative value instead of raising an exception and making exporter crash