Remove unneeded call to db_purge in postrm script and source the debconf file where it is required

distros/debian8/zoneminder.postrm

@@ -17,6 +17,11 @@ apache_remove() {
 
 if [ "$1" = "remove" ] || [ "$1" = "purge" ]; then
 
+    if [ -e /usr/share/debconf/confmodule ]; then
+
+        # Source the debconf stuff
+        . /usr/share/debconf/confmodule
+
         # Deconfigure the web server
         db_get zoneminder/webserver
 
@@ -28,17 +33,13 @@ if [ "$1" = "remove" ] || [ "$1" = "purge" ]; then
                 apache_remove $1
             fi
         done
+    fi
 
     # No need to manually remove the zm database and user, dbconfig take care of this
 fi
 
 if [ "$1" = "purge" ]; then
-    if [ -e /usr/share/debconf/confmodule ]; then
-        # Source the debconf stuff
-        . /usr/share/debconf/confmodule
-        # Remove all package records in the debconf database
-        db_purge
-    fi
+
     # Delete a potential remaining file not managed by debhelper
     rm -f /etc/zm/zm.conf.postinst.bak
 fi