License Plugin: Added a `teardown` to put license back

Since the "Should throw 404 after license deletion" test deletes the license,
a subsequent test run fails for many tests in other components.

This patch adds a `teardown` section to install back a trial development license.

Closes elastic/elasticsearch#2782

Original commit: elastic/x-pack-elasticsearch@45ec5d4244

elasticsearch/x-pack/license-plugin/src/test/resources/rest-api-spec/test/license/20_put_license.yaml

@@ -1,4 +1,11 @@
 ---
+teardown:
+  - do:
+      xpack.license.post:
+        acknowledge: true
+        body: |
+          {"licenses":[{"uid":"894371dc-9t49-4997-93cb-8o2e3r7fa6a8","type":"trial","issue_date_in_millis":1411948800000,"expiry_date_in_millis":1916956799999,"max_nodes":1,"issued_to":"issuedTo","issuer":"issuer","signature":"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"}]}
+---
 "installing and getting license works":
 
     ## current license version