Add benchmark fixture stubs for TRIM and EAR

Relates elastic#18

Author: danielmitterdorfer

fixtures/encryption-at-rest/README.md

@@ -0,0 +1 @@
+Sets up a dm-crypted volume based on the [encrypted_storage Ansible role](https://github.com/elastic/infra/blob/master/ansible/roles/encrypted_storage/README.md) from the infra repo (although we'll need to copy the code from that role to this repo). 

fixtures/encryption-at-rest/setup.yml

@@ -0,0 +1,9 @@
+---
+
+# This is just a NOOP placeholder. In reality we will create the encrypted volume here.
+- hosts: macrobenchmarks-targets
+  tasks:
+  - name: Set up the encrypted data volume
+      become_user: jenkins
+      command: echo "NOOP"
+      when: false

fixtures/encryption-at-rest/teardown.yml

@@ -0,0 +1,9 @@
+---
+
+# This is just a NOOP placeholder. In reality we will replace the encrypted volume again with a plain ext4 volume.
+- hosts: macrobenchmarks-targets
+  tasks:
+  - name: Delete the encrypted data volume
+      become_user: jenkins
+      command: echo "NOOP"
+      when: false

fixtures/trim/README.md

@@ -0,0 +1 @@
+Runs `fstrim` at the beginning of each benchmark to ensure repeatable conditions as [some workloads are quite sensitive](https://www.elastic.co/blog/is-your-elasticsearch-trimmed) w.r.t. trimming. 

fixtures/trim/setup.yml

@@ -0,0 +1,9 @@
+---
+
+# Maybe we need custom permissions for Jenkins in /etc/sudoers.d/ -> update macrobenchmark targets role in infra repo then.
+
+- hosts: macrobenchmarks-targets
+  tasks:
+  - name: Run the TRIM command
+      become_user: jenkins
+      command: /sbin/fstrim --all

fixtures/trim/teardown.yml

@@ -0,0 +1,10 @@
+---
+
+# TRIM is a setup-only fixture. There is nothing to do in teardown. In order to have a consistent structure for all fixtures, we
+# just declare a NOOP fixture here.
+- hosts: macrobenchmarks-targets
+  tasks:
+  - name: Run the NOOP task
+      become_user: jenkins
+      command: echo "NOOP"
+      when: false