Land rapid7#4878, squid_pivot_scanning interpolation fix

Author: wvu

modules/auxiliary/scanner/http/squid_pivot_scanning.rb

@@ -65,7 +65,7 @@ def run_host(target_host)
         manual = false
         #request a non-existent page first to make sure the server doesn't respond with a 200 to everything.
         res_test = send_request_cgi({
-          'uri'          => "http://{datastore['CANARY_IP']}:80",
+          'uri'          => "http://#{datastore['CANARY_IP']}:80",
           'method'       => 'GET',
           'data'  =>      '',
           'version' => '1.0',