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/fsstat.go

@@ -0,0 +1,31 @@
+// +build aix
+
+package perfstat
+
+/*
+#include "c_helpers.h"
+*/
+import "C"
+
+import (
+	"fmt"
+)
+
+func FileSystemStat() ([]FileSystem, error) {
+	var fsinfo *C.struct_fsinfo
+	var nmounts C.int
+
+	fsinfo = C.get_all_fs(&nmounts)
+	if nmounts <= 0 {
+		return nil, fmt.Errorf("No mounts found")
+	}
+
+	fs := make([]FileSystem, nmounts)
+	for i := 0; i < int(nmounts); i++ {
+		f := C.get_filesystem_stat(fsinfo, C.int(i))
+		if f != nil {
+			fs[i] = fsinfo2filesystem(f)
+		}
+	}
+	return fs, nil
+}