TT#28952 Download sha1 file from deb.sipwise.com/files/grml

We are using not stable GRML release so there is no
grml64-small_2018.04.11.iso.sha1 on download.grml.org

Change-Id: I080f8b77d7373c6529164f483f055bf1f7e1c7ef

build_iso.sh

@@ -11,7 +11,7 @@ MR="$3"
 DIST="$4"
 TEMPLATES="templates"
 GRML_URL="${GRML_URL:-https://deb.sipwise.com/files/grml/}"
-GRML_HASH_URL="${GRML_HASH_URL:-http://download.grml.org/}"
+GRML_HASH_URL="${GRML_HASH_URL:-https://deb.sipwise.com/files/grml/}"
 SIPWISE_ISO="sip_provider_${MR}_${DATE}.iso"
 
 usage () {