Allow for specifying root job directory

The finger log streamer will look in the root job dir to
find job logs.

Change-Id: Ib585e04e890cf73bd254d3ba4e7ac3cf01cd342c
diff --git a/zuul/cmd/executor.py b/zuul/cmd/executor.py
index 1893f5a..4f5b61c 100755
--- a/zuul/cmd/executor.py
+++ b/zuul/cmd/executor.py
@@ -79,8 +79,14 @@
 
         self.log = logging.getLogger("zuul.Executor")
 
+        jobroot_dir = None
+        if self.config.has_option('zuul', 'jobroot_dir'):
+            jobroot_dir = os.path.expanduser(
+                self.config.get('zuul', 'jobroot_dir'))
+
         ExecutorServer = zuul.executor.server.ExecutorServer
         self.executor = ExecutorServer(self.config, self.connections,
+                                       jobdir_root=jobroot_dir,
                                        keep_jobdir=self.args.keep_jobdir)
         self.executor.start()