Fix a idmap leak in AssetManager::addSystemOverlays.
And, The fix could also prevent fd leak of idmap.
Test: none
Bug: 32691930
Signed-off-by: Hyangseok Chae <neo.chae@lge.com>
(cherry picked from commit 6a742a38509693f8b39ee9a5ad2803fca12688bf)
Change-Id: Idc4af77db2b0cb739bd6b009b6af0f9123be1aac