package_to_container: change process to uid/gid 0

The OCI spec wants the process uid/gid to be relative to the container's
user namespace. For our simple config.json, this is helpfully always 0.

BUG=none
TEST=container still starts after running package_to_container
CQ-DEPEND=CL:431317

Change-Id: I82182ca168e3574d7105fb07e07d3d4988f58478
Reviewed-on: https://chromium-review.googlesource.com/437714
Commit-Ready: Stephen Barber <smbarber@chromium.org>
Tested-by: Stephen Barber <smbarber@chromium.org>
Reviewed-by: Dylan Reid <dgreid@chromium.org>
diff --git a/generic_container_files/config.json b/generic_container_files/config.json
index 87dd2f6..7fbceed 100644
--- a/generic_container_files/config.json
+++ b/generic_container_files/config.json
@@ -7,8 +7,8 @@
 	"process": {
 		"terminal": @TERMINAL@,
 		"user": {
-			"uid": @USER_UID@,
-			"gid": @USER_GID@
+			"uid": 0,
+			"gid": 0
 		},
 		"args": [
 			"@ARGV@"