Revert "fix comparing string to a number"

This reverts commit 2fcf0222f7.

It was accidentially merged with PR#12 - password aging on CentOS.
I think it is wrong so reverting from now...

common/download.sh

@@ -39,7 +39,7 @@ elif [ ${DISTRIBUTION} = 'fedora' -a "${RELEASE}" = 'rawhide' ]; then
   utils.lxc.create -t fedora --\
                    --release ${RELEASE} \
                    --arch ${ARCH}
-elif [[ ( ${DISTRIBUTION} = 'fedora' ) && ( ${RELEASE} -ge 21 ) ]]; then
+elif [ ${DISTRIBUTION} = 'fedora' -a ${RELEASE} -ge 21 ]; then
   ARCH=$(echo ${ARCH} | sed -e "s/38/68/" | sed -e "s/amd64/x86_64/")
   utils.lxc.create -t fedora --\
                    --release ${RELEASE} \