Set BUILD_TIMEOUT environment variable in zuul_legacy_vars

Jobs that need this expect it as an environment variable.

Update the migration script in case it gets used again.

Change-Id: Ic4d372a795e17a33116d19e9e4603fb5a08fe152

zuul/ansible/filter/zuul_filters.py

@@ -25,7 +25,8 @@ def zuul_legacy_vars(zuul):
                   ZUUL_SHORT_PROJECT_NAME=short_name,
                   ZUUL_PIPELINE=zuul['pipeline'],
                   ZUUL_VOTING=zuul['voting'],
-                  WORKSPACE='/home/zuul/workspace')
+                  WORKSPACE='/home/zuul/workspace',
+                  BUILD_TIMEOUT=str(int(zuul['timeout']) * 1000))
     if 'branch' in zuul:
         params['ZUUL_BRANCH'] = zuul['branch']
 

zuul/cmd/migrate.py

@@ -932,8 +932,6 @@ class Job:
         timeout = self.getTimeout()
         if timeout:
             output['timeout'] = timeout
-            output.setdefault('vars', {})
-            output['vars']['BUILD_TIMEOUT'] = str(timeout * 1000)
 
         if self.nodes:
             if len(self.nodes) == 1: