modsave: check if anything was written
 * only if md5sum is available, should we select it mandatory?
   atm: {{{FREETZ_BUSYBOX_MD5SUM if FREETZ_HAS_AVM_MULTI_ANNEX && ! FREETZ_REMOVE_MULTI_ANNEX_FIRMWARE_DIFFS}}}

git-svn-id: file:///var/svn/freetz/trunk@10491 149334a1-2f27-0410-a3b9-fc62619ac1e6
7390 labor: fix FIRMWARES

git-svn-id: file:///var/svn/freetz/trunk@10492 149334a1-2f27-0410-a3b9-fc62619ac1e6