Remove usages of LPU.savedPatternExists

The correct method to call is isLockPatternEnabled, which
also checks whether we've actually selected a pattern.

Also removes the code for the obsolete pattern enabled setting.

Bug: 18931518
Change-Id: I6f369eb60f8f6bb1e33384cd06534c713ab52e79

src/com/android/settings/ConfirmLockPattern.java

@@ -148,7 +148,7 @@ public class ConfirmLockPattern extends SettingsActivity {
                 // on first launch, if no lock pattern is set, then finish with
                 // success (don't want user to get stuck confirming something that
                 // doesn't exist).
-                if (!mLockPatternUtils.savedPatternExists()) {
+                if (!mLockPatternUtils.isLockPatternEnabled()) {
                     getActivity().setResult(Activity.RESULT_OK);
                     getActivity().finish();
                 }