python: Automatically disable listeners in batch setups

Determine if gem5 is running in a batch environment by checking if
STDIN is wired to a TTY or not. If the simulator is running in a batch
environment, disable all listeners by default. This behavior can be
overridden using the --enable-listeners option.

Change-Id: I404c709135339144216bf08a2769c016c543333c
Signed-off-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-by: Sean McGoogan <sean.mcgoogan@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/2322
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>

src/python/m5/util/__init__.py

@@ -1,3 +1,15 @@
+# Copyright (c) 2016 ARM Limited
+# All rights reserved.
+#
+# The license below extends only to copyright in the software and shall
+# not be construed as granting a license to any other intellectual
+# property including but not limited to intellectual property relating
+# to a hardware implementation of the functionality of the software
+# licensed hereunder.  You may use the software subject to the license
+# terms below provided that you ensure that this notice is replicated
+# unmodified and in its entirety in all distributions of the software,
+# modified or unmodified, in source code or in binary form.
+#
 # Copyright (c) 2008-2009 The Hewlett-Packard Development Company
 # Copyright (c) 2004-2006 The Regents of The University of Michigan
 # All rights reserved.
@@ -195,3 +207,8 @@ def makeDir(path):
             raise AttributeError, "%s exists but is not directory" % path
     else:
         os.mkdir(path)
+
+def isInteractive():
+    """Check if the simulator is run interactively or in a batch environment"""
+
+    return sys.__stdin__.isatty()