Refrain from creating app-search schema unnecessarily.

Calling removeShortcuts() resulted in creating an app-search schema
for every package, even the ones without shortcuts. This behavior is
causing an extra delay when launcher starts.

Bug: 183614316, 183684181
Test: manual
Test: atest ShortcutManagerTest1 ShortcutManagerTest2 |
      ShortcutManagerTest3 ShortcutManagerTest4 ShortcutManagerTest5 |
      ShortcutManagerTest6 ShortcutManagerTest7 ShortcutManagerTest8 |
      ShortcutManagerTest9 ShortcutManagerTest10 ShortcutManagerTest11
Change-Id: I20aaf0d8b78a92c33d22989c9cc35c53fb9b4127