relax neverallow rules on NETLINK_KOBJECT_UEVENT sockets

Netlink uevent sockets are used by the kernel to inform userspace
when certain events occur, for example, when new hardware is added
or removed. This allows userspace to take some action based on those
messages.

Relax the neverallow rule for NETLINK_KOBJECT_UEVENT sockets.
Certain device specific app domains, such as system_app, may have a
need to receive messages from this socket type.

Continue to neverallow NETLINK_KOBJECT_UEVENT sockets for untrusted_app.
These sockets have been the source of rooting attacks in Android
in the past, and it doesn't make sense to expose this to untrusted_apps.

No new SELinux rules are introduced by this change. This is an
adjustment of compile time assertions only.

Bug: 17525863
Change-Id: I3e538dc8096dc23b9678bcd20e3c1e742c21c967
relax appdomain efs_file neverallow rules

During factory provisioning, some manufacturers may need to pull files
from /factory (label efs_file and bluetooth_efs_file) to collect
device specific identifiers such as the mac address, using commands
similar to the following:

  adb shell cat /factory/ssn
  adb shell cat /factory/bt/bd_addr.conf
  adb shell cat /factory/wifi/mac.txt
  adb shell cat /factory/60isn

read-only access to these files is currently disallowed by a
neverallow rule. Relax the rules to allow read-only access to the
shell user if desired.

No new SELinux rules are added or deleted by this change. This is
only a relaxation in what's allowed for vendor specific policy.

Bug: 17600278
Change-Id: I13f33f996c077918dce70a5cff31a87eac436678