tests: suppress output on switcheroo tests

The output from the switcheroo tests is voluminous and
(because it includes timestamps) highly sensitive to
minor changes, leading to extremely large updates to the
reference outputs.  This patch addresses this problem
by suppressing output from the tests.  An internal
parameter can be set to enable the output.  Wiring that
up to a command-line flag (perhaps even the rudimantary
-v/-q options in m5/main.py) is left for future work.

src/python/m5/simulate.py

@@ -218,7 +218,7 @@ def _changeMemoryMode(system, mode):
     else:
         print "System already in target mode. Memory mode unchanged."
 
-def switchCpus(system, cpuList, do_drain=True):
+def switchCpus(system, cpuList, do_drain=True, verbose=True):
     """Switch CPUs in a system.
 
     By default, this method drains and resumes the system. This
@@ -238,7 +238,10 @@ def switchCpus(system, cpuList, do_drain=True):
     Keyword Arguments:
       do_drain -- Perform a drain/resume of the system when switching.
     """
-    print "switching cpus"
+
+    if verbose:
+        print "switching cpus"
+
     if not isinstance(cpuList, list):
         raise RuntimeError, "Must pass a list to this function"
     for item in cpuList: