core: Use real security patch level property

The standard platform security patch level property may not reflect the
real patch level due to SafetyNet hacks, so we need to check the custom
"real" property to show the correct patch level to the user (and most
apps).

Change-Id: I18f8b6812335f132a935e0cfc04523cf693d1101

core/java/android/os/Build.java

@@ -267,7 +267,7 @@ public static class VERSION {
          * most recently applied a security patch.
          */
         public static final String SECURITY_PATCH = SystemProperties.get(
-                "ro.build.version.security_patch", "");
+                "ro.build.version.real_security_patch", "");
 
         /**
          * The user-visible SDK version of the framework in its raw String