fix: do not probe for power-meters when disabled

Previously, when DISABLE_POWER_METER is set, kepler would still probe
system for power-meters resulting in kepler_node_info to produce
incorrect results for components_power_source and platform_power_source.
E.g.
kepler_node_info{
  components_power_source="rapl-sysfs",
  cpu_architecture="Skylake",
  instance="kepler-latest:8888",
  job="latest",
  platform_power_source="acpi",
  source="os"
}

The commit fixes this to use the fake power-meters so that kepler_node_info
now shows
```
kepler_node_info{components_power_source="estimator",
  cpu_architecture="Skylake",
  instance="kepler-dev:8888",
  job="dev",
  platform_power_source="none",
  source="os"
}
```

Signed-off-by: Sunil Thaha <[email protected]>

pkg/sensors/components/power.go

@@ -48,6 +48,12 @@ var (
 )
 
 func InitPowerImpl() {
+	if !enabled {
+		klog.V(1).Infoln("System power collection is disabled, using estimate method")
+		powerImpl = &source.PowerEstimate{}
+		return
+	}
+
 	sysfsImpl := &source.PowerSysfs{}
 	if sysfsImpl.IsSystemCollectionSupported() /*&& false*/ {
 		klog.V(1).Infoln("use sysfs to obtain power")

pkg/sensors/platform/power.go

@@ -37,8 +37,7 @@ type powerInterface interface {
 }
 
 // dummy satisfies the powerInterface and can be used as the default NOP source
-type dummy struct {
-}
+type dummy struct{}
 
 func (dummy) GetName() string {
 	return "none"
@@ -47,6 +46,7 @@ func (dummy) GetName() string {
 func (dummy) IsSystemCollectionSupported() bool {
 	return false
 }
+
 func (dummy) StopPower() {
 }
 
@@ -60,6 +60,12 @@ var (
 )
 
 func InitPowerImpl() {
+	if !enabled {
+		klog.V(1).Infoln("System power collection is disabled, using dummy method")
+		powerImpl = &dummy{}
+		return
+	}
+
 	// switch the platform power collector source to hmc if the system architecture is s390x
 	// TODO: add redfish or ipmi as well.
 	if runtime.GOARCH == "s390x" {