dist/ubuntu: Install wget package if it's not available

The build scripts use wget so make sure it's actually installed on the
machine.

Message-Id: <1458554706-14558-1-git-send-email-penberg@scylladb.com>

dist/ubuntu/build_deb.sh

@@ -22,6 +22,9 @@ fi
 if [ ! -f /usr/bin/add-apt-repository ]; then
     sudo apt-get -y install software-properties-common
 fi
+if [ ! -f /usr/bin/wget ]; then
+    sudo apt-get -y install wget
+fi
 
 RELEASE=`lsb_release -r|awk '{print $2}'`
 CODENAME=`lsb_release -c|awk '{print $2}'`