init: remove support for disabled SELinux

Remove support for androidboot.selinux=disabled. Running with SELinux
disabled is not a supported configuration anymore. SELinux must be
in enforcing in shipping devices, but we also support permissive for
userdebug/eng builds.

Don't try security_setenforce() if we're already in enforcing mode.
A kernel compiled without CONFIG_SECURITY_SELINUX_DEVELOP does
not have a permissive mode, so the kernel will already be enforcing
once the policy is loaded.

Bug: 19702273
Change-Id: I07525a017ddb682020ec0d42e56a2702c053bdeb
diff --git a/init/Android.mk b/init/Android.mk
index 4bd4f3d..0dc257d 100644
--- a/init/Android.mk
+++ b/init/Android.mk
@@ -5,9 +5,9 @@
 # --
 
 ifneq (,$(filter userdebug eng,$(TARGET_BUILD_VARIANT)))
-init_options += -DALLOW_LOCAL_PROP_OVERRIDE=1 -DALLOW_DISABLE_SELINUX=1
+init_options += -DALLOW_LOCAL_PROP_OVERRIDE=1 -DALLOW_PERMISSIVE_SELINUX=1
 else
-init_options += -DALLOW_LOCAL_PROP_OVERRIDE=0 -DALLOW_DISABLE_SELINUX=0
+init_options += -DALLOW_LOCAL_PROP_OVERRIDE=0 -DALLOW_PERMISSIVE_SELINUX=0
 endif
 
 init_options += -DLOG_UEVENTS=0