use SystemClock.elapsedRealtime() everywhere

Signed-off-by: tobiasKaminsky <tobias@kaminsky.me>

src/main/java/com/owncloud/android/authentication/PassCodeManager.java

@@ -125,7 +125,7 @@ public final class PassCodeManager {
     }
 
     private boolean passCodeShouldBeRequested(Long timestamp) {
-        return (System.currentTimeMillis() - timestamp) > PASS_CODE_TIMEOUT &&
+        return (SystemClock.elapsedRealtime() - timestamp) > PASS_CODE_TIMEOUT &&
             visibleActivitiesCounter <= 0 && isPassCodeEnabled();
     }
 
@@ -134,7 +134,7 @@ public final class PassCodeManager {
     }
 
     private boolean deviceCredentialsShouldBeRequested(Long timestamp, Activity activity) {
-        return (System.currentTimeMillis() - timestamp) > PASS_CODE_TIMEOUT && visibleActivitiesCounter <= 0 &&
+        return (SystemClock.elapsedRealtime() - timestamp) > PASS_CODE_TIMEOUT && visibleActivitiesCounter <= 0 &&
             deviceCredentialsAreEnabled(activity);
     }