Install Elasticsearch 5.3.3 for Travis

5.4 has a bug in testing existence of aliases which causes tests to fail: https://github.com/elastic/elasticsearch/issues/24644

scripts/travis/install_elasticsearch5.sh

@@ -3,7 +3,6 @@
 sudo sysctl -w vm.max_map_count=262144
 
 sudo apt-get autoremove --purge elasticsearch
-wget -qO - https://artifacts.elastic.co/GPG-KEY-elasticsearch | sudo apt-key add -
-echo "deb https://artifacts.elastic.co/packages/5.x/apt stable main" | sudo tee -a /etc/apt/sources.list.d/elastic-5.x.list
-sudo apt-get update && sudo apt-get install elasticsearch -y
+wget -P /tmp/ https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-5.3.3.deb
+sudo dpkg -i /tmp/elasticsearch-5.3.3.deb
 sudo service elasticsearch start