Ansible launcher: fix timeout var

We reassigned the timeout value over top of the dictionary.  This
leaves the dictionary alone so it can be reused.

Change-Id: I4bb2fb24eecea5ba28ac2bb78fb477de6236331a
diff --git a/zuul/launcher/ansiblelaunchserver.py b/zuul/launcher/ansiblelaunchserver.py
index af6eac1..87898b6 100644
--- a/zuul/launcher/ansiblelaunchserver.py
+++ b/zuul/launcher/ansiblelaunchserver.py
@@ -999,10 +999,10 @@
         timeout_var = None
         for wrapper in jjb_job.get('wrappers', []):
             if isinstance(wrapper, dict):
-                timeout = wrapper.get('build-timeout', {})
-                if isinstance(timeout, dict):
-                    timeout = timeout.get('timeout')
-                    timeout_var = timeout.get('timeout-var', None)
+                build_timeout = wrapper.get('build-timeout', {})
+                if isinstance(build_timeout, dict):
+                    timeout_var = build_timeout.get('timeout-var', None)
+                    timeout = build_timeout.get('timeout')
                     if timeout:
                         timeout = timeout * 60
         if not timeout: