Drop supplementary groups for child zygotes. am: 5a452627 am: 694a2b95 am:...

Drop supplementary groups for child zygotes. am: 5a452627 am: 694a2b95 am: abe8b3d9 am: 2f003e1b

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/11689582

Change-Id: Ice9e3f374650f2c383845bbdcae36296c1f80def