added sudo to apt-get update

Step 3 : RUN  apt-get update -y  && tar xzf aerospike.tgz  && cd aerospike-server-community-*  && sudo dpkg -i aerospike-server-*
 ---> Running in 49c8063be48e
2014/08/23 15:54:40 permission denied
2014/08/23 21:24:41 The command [/bin/sh -c apt-get update -y  && tar xzf aerospike.tgz  && cd aerospike-server-community-*  && sudo dpkg -i aerospike-server-*] returned a non-zero code: 1