UserController/Manager loglines

Adds a few more important, infrequent loglines to
UserController and UserManager.

Also marks their private methods as private (if not already so marked)
to make it clearer which methods are called from external classes.

Test: compiles
Test: atest UserManagerServiceTest UserManagerServiceUserInfoTest UserManagerServiceUserTypeTest UserManagerTest UserSystemPackageInstallerTest UserControllerTest
Change-Id: I67340178c8576461d0adde395c90215d85d1f56e