Change Cpu.Get() on Windows to not use floating point artimetic

Backport of elastic#1128 to 1.2.1

CHANGELOG.asciidoc

@@ -92,6 +92,7 @@ https://github.com/elastic/beats/compare/v1.1.2...v1.2.0[View commits]
 *Topbeat*
 
 - Add the command line used to start processes {issue}533[533]
+- Fix issue with cpu.system_p being greater than 1 on Windows {pull}1128[1128]
 
 *Filebeat*
 

topbeat/beat/sigar.go

@@ -5,7 +5,7 @@ import (
 	"strings"
 	"time"
 
-	"github.com/elastic/gosigar"
+	sigar "github.com/elastic/gosigar"
 )
 
 type SystemLoad struct {

topbeat/beat/topbeat.go

@@ -7,7 +7,7 @@ import (
 	"strconv"
 	"time"
 
-	"github.com/elastic/gosigar"
+	sigar "github.com/elastic/gosigar"
 
 	"github.com/elastic/beats/libbeat/beat"
 	"github.com/elastic/beats/libbeat/cfgfile"
@@ -383,9 +383,9 @@ func (t *Topbeat) addCpuPercentage(t2 *CpuTimes) {
 		calculate := func(field2 uint64, field1 uint64) float64 {
 
 			perc := 0.0
-			delta := field2 - field1
+			delta := int64(field2 - field1)
 			perc = float64(delta) / float64(all_delta)
-			return Round(perc, .5, 2)
+			return Round(perc, .5, 4)
 		}
 
 		t2.UserPercent = calculate(t2.User, t1.User)
@@ -405,9 +405,9 @@ func (t *Topbeat) addCpuPercentageList(t2 []CpuTimes) {
 		calculate := func(field2 uint64, field1 uint64, all_delta uint64) float64 {
 
 			perc := 0.0
-			delta := field2 - field1
+			delta := int64(field2 - field1)
 			perc = float64(delta) / float64(all_delta)
-			return Round(perc, .5, 2)
+			return Round(perc, .5, 4)
 		}
 
 		for i := 0; i < len(t1); i++ {
@@ -451,7 +451,7 @@ func (t *Topbeat) addProcCpuPercentage(proc *Process) {
 
 		t.procsMap[proc.Pid] = proc
 
-		proc.Cpu.UserPercent = Round(perc, .5, 2)
+		proc.Cpu.UserPercent = Round(perc, .5, 4)
 
 	}
 }

topbeat/beat/topbeat_test.go

@@ -93,8 +93,8 @@ func TestCpuPercentage(t *testing.T) {
 
 	beat.addCpuPercentage(&cpu2)
 
-	assert.Equal(t, cpu2.UserPercent, 0.95)
-	assert.Equal(t, cpu2.SystemPercent, 0.04)
+	assert.Equal(t, cpu2.UserPercent, 0.9502)
+	assert.Equal(t, cpu2.SystemPercent, 0.0448)
 }
 
 func TestProcMemPercentage(t *testing.T) {
@@ -146,5 +146,5 @@ func TestProcCpuPercentage(t *testing.T) {
 	beat.procsMap[p1.Pid] = &p1
 
 	beat.addProcCpuPercentage(&p2)
-	assert.Equal(t, p2.Cpu.UserPercent, 3.46)
+	assert.Equal(t, p2.Cpu.UserPercent, 3.459)
 }