Updating Security String to 2017-09-01 Bug:63846344
(cherry picked from commit f1c17f17ff96d2a9705d6b7a003374c9f83ba14d)

Change-Id: Ib85e763e92585becf4e79419b721407a00ec6d00
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index c4d926a..f10e04d 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -165,7 +165,7 @@
     #  It must be of the form "YYYY-MM-DD" on production devices.
     #  It must match one of the Android Security Patch Level strings of the Public Security Bulletins.
     #  If there is no $PLATFORM_SECURITY_PATCH set, keep it empty.
-      PLATFORM_SECURITY_PATCH := 2017-08-05
+      PLATFORM_SECURITY_PATCH := 2017-09-01
 endif
 
 ifndef PLATFORM_BASE_OS