Change to using gopsutil for cross-OS process ops

Instead of trying to write out own code to do basic process
operations (e.g. checking if a PID is still running in a multi-OS
friendly manner), use shirou/gopsutil, a multi-platform library
that should abstract all the complexity away. Unlike our previous
approach on Windows, this one should actually work.

Signed-off-by: Matt Heon <mheon@redhat.com>

vendor/github.com/power-devops/perfstat/lparstat.go

@@ -0,0 +1,26 @@
+// +build aix
+
+package perfstat
+
+/*
+#cgo LDFLAGS: -lperfstat
+
+#include <libperfstat.h>
+*/
+import "C"
+
+import (
+	"fmt"
+)
+
+func PartitionStat() (*PartitionConfig, error) {
+	var part C.perfstat_partition_config_t
+
+	rc := C.perfstat_partition_config(nil, &part, C.sizeof_perfstat_partition_config_t, 1)
+	if rc != 1 {
+		return nil, fmt.Errorf("perfstat_partition_config() error")
+	}
+	p := perfstatpartitionconfig2partitionconfig(part)
+	return &p, nil
+
+}