Update Security String to 2017-05-01 on nyc-dev

Bug:34137924
(cherry picked from commit 573e7e75cab017946716fbd4ba01cbd8e7563478)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 86a67a1..1e10edc 100644
--- a/core/version_defaults.mk
+++ b/core/version_defaults.mk
@@ -114,7 +114,7 @@
     #  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 := 2017-04-05
+      PLATFORM_SECURITY_PATCH := 2017-05-01
 endif
 
 ifeq "" "$(PLATFORM_BASE_OS)"