Make helper fail is OSFAMILY property is missing

Also did a minor cleanup in AssignHostname task

snf-image-helper/snf-image-helper.in

@@ -75,6 +75,11 @@ fi
 trap '{ umount "$target"; }' ERR
 
 if [ -z "$SNF_IMAGE_PROPERTY_EXCLUDE_ALL_TASKS" ]; then
+
+    if [[ ! "$SNF_IMAGE_PROPERTY_OSFAMILY" =~ ^(linux|windows)$ ]]; then
+        log_error "Supported values for OSFAMILY propertry are: linux|windows"
+    fi
+
     # Redirect standard error to standard output,
     # prepend a timestamp before each line of output.
     echo "Execute all snf-image tasks...."

snf-image-helper/tasks/50AssignHostname.in

@@ -56,14 +56,13 @@ linux_hostname() {
         redhat)
             sed -ie "s/HOSTNAME=.*$/HOSTNAME=$hostname/g" "$target/etc/sysconfig/network";;
         slackware|suse)
-        #local domain=$(sed -e 's/^[^\.]*//g' < /etc/HOSTNAME)
-        
-        # In slackware hostname and domain name are joined together. For now I
-        # will not retain the domain name.
-        
-        echo "$hostname" > "${target}/etc/HOSTNAME";;
-    gentoo)
-        sed -ie "s/\(\(HOSTNAME\)\|\(hostname\)\)=.*$/\1=\"$hostname\"/" "$target/etc/conf.d/hostname";;
+            #local domain=$(sed -e 's/^[^\.]*//g' < /etc/HOSTNAME)
+
+            # In slackware hostname and domain name are joined together. For now
+            # I will not retain the domain name.
+            echo "$hostname" > "${target}/etc/HOSTNAME";;
+        gentoo)
+            sed -ie "s/\(\(HOSTNAME\)\|\(hostname\)\)=.*$/\1=\"$hostname\"/" "$target/etc/conf.d/hostname";;
     esac
 
     # Some Linux distributions assign the hostname to 127.0.1.1 in order to be