Use GSI-specific init script to detect GSI image. am: 9772f86fb7 am: c7cbc3a1de

Original change: https://android-review.googlesource.com/c/platform/system/gsid/+/3206391

Change-Id: Icd5fc564d1cdcb304ffba78b45c7fc9f307350c5
Signed-off-by: Automerger Merge Worker <[email protected]>