correct debian postinst error

debian/postinst

@@ -3,10 +3,13 @@ set -e
 
 case "$1" in
     configure)
-        [ -e /media ] || mkdir /media
+        if [ ! -e /media ]; then
+            mkdir /media
+        fi
 
         # confine udevil execution to plugdev group members?
-    if (( 0 )); then
+        UDEVIL_USE_PLUGDEV=0
+        if [ $UDEVIL_USE_PLUGDEV -ne 0 ]; then
             for prog in /usr/bin/udevil; do
                 if ! dpkg-statoverride --list $prog > /dev/null; then
                         if ! getent group plugdev > /dev/null; then
@@ -30,6 +33,9 @@ case "$1" in
         ;;
 esac
 
+# dh_installdeb will replace this with shell code automatically
+# generated by other debhelper scripts.
+
 #DEBHELPER#
 
 exit 0

debian/postrm

@@ -1,6 +1,15 @@
 #! /bin/sh
 set -e
 
-if [ "$1" == "purge" ]; then
+case "$1" in
+    purge)
         rm -rf /etc/udevil
-fi
+    ;;
+esac
+
+# dh_installdeb will replace this with shell code automatically
+# generated by other debhelper scripts.
+
+#DEBHELPER#
+
+exit 0