sockets: Add a function to disable all listening sockets.

When invoking several copies of m5 on the same machine at the same
time, there can be a race for TCP ports for the terminal connections
or remote gdb.  Expose a function to disable those ports, and have the
regression scripts disable them.  There are some SimObjects that have
no other function than to be used with ports (NativeTrace and
EtherTap), so they will panic if the ports are disabled.

tests/run.py

@@ -26,7 +26,12 @@
 #
 # Authors: Steve Reinhardt
 
-import os, sys
+import os
+import sys
+import m5
+
+# Since we're in batch mode, dont allow tcp socket connections
+m5.disableAllListeners()
 
 # single "path" arg encodes everything we need to know about test
 (category, name, isa, opsys, config) = sys.argv[1].split('/')
@@ -57,8 +62,7 @@ execfile(os.path.join(tests_root, 'configs', config + '.py'))
 
 # set default maxtick... script can override
 # -1 means run forever
-from m5 import MaxTick
-maxtick = MaxTick
+maxtick = m5.MaxTick
 
 # tweak configuration for specific test