Ensure a reliable way to kill ghost containers on reboot

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

system/proc.go

@@ -0,0 +1,26 @@
+package system
+
+import (
+	"io/ioutil"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+// look in /proc to find the process start time so that we can verify
+// that this pid has started after ourself
+func GetProcessStartTime(pid int) (string, error) {
+	data, err := ioutil.ReadFile(filepath.Join("/proc", strconv.Itoa(pid), "stat"))
+	if err != nil {
+		return "", err
+	}
+	parts := strings.Split(string(data), " ")
+	// the starttime is located at pos 22
+	// from the man page
+	//
+	// starttime %llu (was %lu before Linux 2.6)
+	// (22)  The  time the process started after system boot.  In kernels before Linux 2.6, this
+	// value was expressed in jiffies.  Since Linux 2.6, the value is expressed in  clock  ticks
+	// (divide by sysconf(_SC_CLK_TCK)).
+	return parts[22-1], nil // starts at 1
+}