When running a single test case, lldb.SBDebugger.Terminate() is not being called
because unittest.main() calls sys.exit() before returning.  Fixed by registering
an exit handler for this situation.

llvm-svn: 110379
diff --git a/lldb/test/command_source/TestCommandSource.py b/lldb/test/command_source/TestCommandSource.py
index 59a97e5..23e5815 100644
--- a/lldb/test/command_source/TestCommandSource.py
+++ b/lldb/test/command_source/TestCommandSource.py
@@ -30,6 +30,7 @@
 
 
 if __name__ == '__main__':
+    import atexit
     lldb.SBDebugger.Initialize()
+    atexit.register(lambda: lldb.SBDebugger.Terminate())
     unittest.main()
-    lldb.SBDebugger.Terminate()