vidjil-server.postinst fix issue with folder creation

packaging/server/debian/vidjil-server.postinst

@@ -309,14 +309,12 @@ case "$1" in
         sudo -u www-data python -c "from gluon.main import save_password; save_password('$password',443)"
 
         if [ ! -d /mnt/vidjil_data/upload ] ; then
-            mkdir /mnt/vidjil_data/upload
-            mkdir /mnt/vidjil_data/upload/uploads
+            mkdir -p /mnt/vidjil_data/upload/uploads
             chown -R www-data:www-data /mnt/vidjil_data/upload
         fi
 
         if [ ! -d /mnt/vidjil_data/result ] ; then
-            mkdir /mnt/vidjil_data/result
-            mkdir /mnt/vidjil_data/result/results
+            mkdir -p/mnt/vidjil_data/result/results
             chown -R www-data:www-data /mnt/vidjil_data/result
         fi