cmsdk: Add PerformanceManager tests, Change target permission.

Since PerformanceManager is strictly a CyanogenMod construct,
  it doesn't make sense to enforce the interfaces with an android
  specific permission (even though the implementation is delegated
  to power manager). To keep consistency with the other api's,
  modify the enforcing permission to a cm specific declaration.

  Also add test cases for the PerformanceManager public interfaces.

Change-Id: I430b69dbee73bf94bb60932d1942ab97e3ba193e

src/java/cyanogenmod/power/PerformanceManager.java

@@ -94,7 +94,8 @@ public class PerformanceManager {
         return sInstance;
     }
 
-    private static IPerformanceManager getService() {
+    /** @hide */
+    public static IPerformanceManager getService() {
         if (sService != null) {
             return sService;
         }