Add 7.8 job to Jenkins

Author: sethmlarson

.ci/jobs/elastic+elasticsearch-py+7.8.yml

@@ -0,0 +1,12 @@
+---
+- job:
+    name: elastic+elasticsearch-py+7.8
+    display-name: 'elastic / elasticsearch-py # 7.8'
+    description: Testing the elasticsearch-py 7.8 branch.
+    junit_results: "*-junit.xml"
+    parameters:
+    - string:
+        name: branch_specifier
+        default: refs/heads/7.7
+        description: the Git branch specifier to build (<branchName>, <tagName>,
+          <commitId>, etc.)