Give fastbootd permission to mount and write to /metadata/gsi.

This is needed to check for the presence of certain bits, like,
snapshots, a scratch partition, or a DSU installation, as well as to
create status files (which libfiemap uses to track state).

Bug: 134949511
Test: adb remount; fastboot flash system
Change-Id: I50c10647a5793e4c0f35c3dd32de0bc036921914
1 file changed