Implement oboard diagnostics admin API (#9024)

- Implement a graph algorithm to test network bandwidth from every 
  node to every other node
- Saturate any network bandwidth adaptively, accounting for slow 
  and fast network capacity
- Implement parallel drive OBD tests
- Implement a paging mechanism for OBD test to provide periodic updates to client
- Implement Sys, Process, Host, Mem OBD Infos

pkg/madmin/obd_freebsd.go

@@ -0,0 +1,7 @@
+package madmin
+
+// ServerDiskHwOBDInfo - Includes usage counters, disk counters and partitions
+type ServerDiskHwOBDInfo struct {
+	Addr  string `json:"addr"`
+	Error string `json:"error,omitempty"`
+}