Setup salt provisioning

This commit performs salt provisioning setup by adding salt master to
the salt VM and salt minion to all VMs. An /etc/hosts entry for the salt
master is added using a shell provisioner. No salt executions are
performed yet.

scripts/add_salt_to_etc_hosts.sh

@@ -0,0 +1,22 @@
+#!/bin/sh
+
+set -e
+
+ip_address="172.16.4.10"
+host_name="salt.gva.dev"
+
+matches_in_host="$(grep -n $host_name /etc/hosts | cut -f1 -d:)"
+host_entry="${ip_address} ${host_name} salt"
+
+if [ ! -z "$matches_in_host" ]
+then
+    echo "Updating existing hosts entry"
+
+    echo $matches_in_host | while read -r line_number; do
+        sed -i "${line_number}s/.*/${host_entry}/" /etc/hosts
+    done
+else
+    echo "Adding new hosts entry"
+
+    echo "${host_entry}" >> /etc/hosts 
+fi