HadoopHttp library class doesn't recurse JSON fields, misses metrics

[HariSekhon]

HadoopHttp library class doesn't recursely walk the JMX JSON properly for Hadoop / HBase and therefore doesn't extract all the metrics.

For example it doesn't extract LastGCInfo duration which is really important for monitoring GC Pause times (GCTimeMillis just doesn't cut it), since the 'value' of the field is json it fails the is_numeric() check from utils and skips it entirely:

  }, {
    "name" : "java.lang:type=GarbageCollector,name=G1 Young Generation",
    "modelerType" : "sun.management.GarbageCollectorImpl",
    "LastGcInfo" : {
      "GcThreadCount" : 24,
      "duration" : 265,

This will affect all the Hadoop and HBase plugins.

[HariSekhon]

Looks like there is a patch pull request in #375 since last Oct but nobody has reviewed it.