Allow app_zygote to read zygote_tmpfs.

app_zygote inherits tmpfs files from zygote, and needs to be able to
stat them after fork.

Bug: 192634726
Bug: 192572973
Bug: 119800099
Test: forrest
Ignore-AOSP-First: cherry pick of https://r.android.com/1753279
Change-Id: I6ddf433dbbf4a894fcb6d35c0cb723444d360e47
2 files changed