TASK: Update Elasticsearch version for tests

Author: kdambekalns

.travis.yml

@@ -15,7 +15,7 @@ matrix:
 before_install:
   - export NEOS_TARGET_VERSION=4.0
   - cd ..
-  - if [ "$ES" = 5 ]; then wget --no-check-certificate https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-5.6.8.zip && unzip elasticsearch-5.6.8.zip && mv elasticsearch-5.6.8 elasticsearch; fi
+  - if [ "$ES" = 5 ]; then wget --no-check-certificate https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-5.6.15.zip && unzip elasticsearch-5.6.15.zip && mv elasticsearch-5.6.15 elasticsearch; fi
   - cd elasticsearch
   - bin/elasticsearch -d
   - cd ..