Fixed use of incorect var for OS detection

SubModules/redis/preconf.sh

@@ -1,6 +1,6 @@
 #!/bin/bash
 
-if [ "$shortdist" = "ubu1804" ] || [ "$osrel" = "ubu2004" ] || [ "$osrel" = "deb10" ] ; then
+if [ "$shortdist" = "ubu1804" ] || [ "$shortdist" = "ubu2004" ] || [ "$shortdist" = "deb10" ] ; then
 # Debian/Ubunbtu redis variables
     redisService=redis-server