Fix the bug that user setting is removed when switching

The user is only started once and will not trigger onUserStarting in
subsequent switching, we should not remove it from the mapping otherwise
all the package configuration will get lost and game mode can't be set.

Bug: 258724297
Test: atest GameManagerServiceTests
Change-Id: I79fecd6f0ef5d751ad4fbadb8cb3cc43df8f3bce