Read the log file as binary in zuul_console

It gets decoded as utf-8 on the other side of the socket, and it's being
written to the file as utf-8 - so there's not reason to read it in to a
string before sending it over the wire.

Change-Id: Iad3d33108835fad3ceae0eec38985659449a6452

zuul/ansible/library/zuul_console.py

@@ -59,7 +59,7 @@ def daemonize():
 class Console(object):
     def __init__(self, path):
         self.path = path
-        self.file = open(path)
+        self.file = open(path, 'rb')
         self.stat = os.stat(path)
         self.size = self.stat.st_size