Update default suite

netboot.sh

@@ -93,7 +93,7 @@ TRANSPORT=${TRANSPORT:-http}
 MIRROR=${MIRROR:-deb.debian.org}
 DIRECTORY=${DIRECTORY:-/debian}
 ARCH=$(dpkg --print-architecture)
-SUITE=${SUITE:-stable}
+SUITE=${SUITE:-stretch}
 USERNAME=${USERNAME:-debian}
 TIMEZONE=${TIMEZONE:-UTC}
 NTPSERVER=${NTPSERVER:-pool.ntp.org}