Introduce bashate

This commit introduces bashate[0] which is a code style checker for bash
scripts. We already have some bash scripts in Tempest repo. So, it might
be good to check the style automatically.

Some scripts under the tools directory are also fixed due to the bashate
violation.

Change-Id: I07820f10387552f93a9d8891b58a8c7fcdb83046
diff --git a/.zuul.yaml b/.zuul.yaml
index cdc63a7..fad4ed0 100644
--- a/.zuul.yaml
+++ b/.zuul.yaml
@@ -778,6 +778,7 @@
         - tempest-full-test-account-no-admin-py3:
             voting: false
             irrelevant-files: *tempest-irrelevant-files
+        - openstack-tox-bashate
     gate:
       jobs:
         - tempest-slow-py3: