/dev/[kvm|vhost-vsock] are owned by system

/dev/kvm and /dev/vhost-vsock are used by crosvm. Previously, it ran as
a custom UID `virtualizationservice`. However, this prevented us from
applying task profiles to the crosvm process because joining a process
to a cgroup requires system UID.

Now, crosvm (and its parent virtualizationservice as well) runs in
system UID. Therefore, the ownership of two device files are also
updated accorgly.

BUG=b:216788146
BUG=b:223790172
Test: watch TH

Change-Id: I1f63a12532d3a2cb5724291dbbb40210bd7c9203
diff --git a/rootdir/ueventd.rc b/rootdir/ueventd.rc
index 3101974..a140c8c 100644
--- a/rootdir/ueventd.rc
+++ b/rootdir/ueventd.rc
@@ -67,9 +67,8 @@
 # CDMA radio interface MUX
 /dev/ppp                  0660   radio      vpn
 
-# Virtualization is managed by VirtualizationService.
-/dev/kvm                  0600   virtualizationservice root
-/dev/vhost-vsock          0600   virtualizationservice root
+/dev/kvm                  0600   system     system
+/dev/vhost-vsock          0600   system	    system
 
 # sysfs properties
 /sys/devices/platform/trusty.*      trusty_version        0440  root   log