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/lufia/plan9stats/int.go

@@ -0,0 +1,31 @@
+package stats
+
+import (
+	"strconv"
+)
+
+type intParser struct {
+	err error
+}
+
+func (p *intParser) ParseInt(s string, base int) int {
+	if p.err != nil {
+		return 0
+	}
+	var n int64
+	n, p.err = strconv.ParseInt(s, base, 0)
+	return int(n)
+}
+
+func (p *intParser) ParseInt64(s string, base int) int64 {
+	if p.err != nil {
+		return 0
+	}
+	var n int64
+	n, p.err = strconv.ParseInt(s, base, 64)
+	return n
+}
+
+func (p *intParser) Err() error {
+	return p.err
+}