Update Security String to 2017-04-01 on nyc-dev

Bug:35314737
(cherry picked from commit 93c1a722c2c579a7360a160c77c754382018f348)
diff --git a/core/version_defaults.mk b/core/version_defaults.mk
index 3e3814a..9d67166 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 := 2017-03-05
+      PLATFORM_SECURITY_PATCH := 2017-04-01
 endif
 
 ifeq "" "$(PLATFORM_BASE_OS)"