TT#87854 Lower grml2usb version

This is revert of commit aadbef82b0

The version 0.18.1 fails during the building of mr8.5.1:
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10:59:57 Executing grml2usb version v0.18.1 (git)
10:59:57 Checking for boot flag
10:59:57 Fatal: /tmp/grml2iso.tmp/cddir: unrecognised disk label
===============================

So restore working 0.17.0 version.

Change-Id: Ib5b3369152378dc3aeb7282d098383c5df82904d

build_iso.sh

@@ -16,7 +16,7 @@ TEMPLATES="templates"
 GRML_URL="${GRML_URL:-https://deb.sipwise.com/deployment-iso/grml/}"
 GRML_HASH_URL="${GRML_HASH_URL:-https://deb.sipwise.com/deployment-iso/grml/}"
 SIPWISE_ISO="sip_provider_${MR}_${DATE}.iso"
-GRML2USB_VERSION='v0.18.1'
+GRML2USB_VERSION='v0.17.0'
 
 usage () {
   echo "Usage: $0 compat <grml.iso> <mr version> <Debian dist>"