Don't duplicate data dir

Dockerfile

@@ -18,6 +18,7 @@ RUN VERSION=`cat /tmp/VERSION` && \
 
 VOLUME ["/data"]
 ENV HOME /data
+ENV DATA /data
 WORKDIR /data
 
 EXPOSE 8332 8333

bin/init

@@ -1,7 +1,6 @@
 #!/bin/bash
 
-DATA_DIR=/data
-CONF=${DATA_DIR}/vertcoin.conf
+CONF=${DATA}/vertcoin.conf
 
 if [ ! -e "${CONF}" ]; then
   echo "disablewallet=1
@@ -12,4 +11,4 @@ rpcuser=rpc
 rpcpassword=`dd if=/dev/urandom bs=18 count=1 2>/dev/null | base64`" > "${CONF}"
 fi
 
-exec vertcoind -datadir=${DATA_DIR} -conf=${CONF} "$@"
+exec vertcoind -datadir=${DATA} -conf=${CONF} "$@"