Ignore ro.adb.secure in user builds.

Require authorization by default, and remove the ability to override
that in user builds. (userdebug and eng are still free to do whatever
they want.)

Bug: http://b/21862859
Change-Id: Ibf8af375be5bf1141c1ad481eee7a59fb10a7adb
(cherry picked from commit 5cba504215ea91187cc36ec7aec5dce1b0f4b0fe)
diff --git a/adb/adb_main.cpp b/adb/adb_main.cpp
index 3f88d13..45a2158 100644
--- a/adb/adb_main.cpp
+++ b/adb/adb_main.cpp
@@ -239,10 +239,11 @@
     // descriptor will always be open.
     adbd_cloexec_auth_socket();
 
-    property_get("ro.adb.secure", value, "0");
-    auth_enabled = !strcmp(value, "1");
-    if (auth_enabled)
-        adbd_auth_init();
+    if (ALLOW_ADBD_NO_AUTH && property_get_bool("ro.adb.secure", 0) == 0) {
+        auth_required = false;
+    }
+
+    adbd_auth_init();
 
     // Our external storage path may be different than apps, since
     // we aren't able to bind mount after dropping root.