Some pages that extend ManageApplications always display a loading
spinner when entering them. This is caused by that it takes over
100 ms to load all apps and to sort the apps. In addition, the task of
loading all apps might be invoked twice, which caused loading time
increasing.
This CL is to make sure the task of loading all apps execute only once
in those pages that extend ManageApplications.
Bug: 222985623
Test: manual test
Change-Id: I3b15bf2eee2a4c220f42da39a29f0014cc620898
fdbf748dc0