Do not overwrite isEmbedded

On devices with HAL<1.2 the UiccSlot.isEmbedded information is incorrect
(e.g. the platform does not know when eUICCs are eUICCs and just treats
them like regular UICCs).

Bug: 122768800
Test: manual
Change-Id: I8cfe21392f1d76dba8553032f7a27b8214adb82a