scripts: runners: openocd: Enable thread awareness

Zephyr thread awareness is available for openocd but boards don't
have debuggers configuration.  This configure OpenOCD runner
automatically to complete configuration.

User still require enable CONFIG_DEBUG_THREAD_INFO=y to visualize
thread debug information.

Signed-off-by: Gerson Fernando Budke <nandojve@gmail.com>
diff --git a/scripts/west_commands/run_common.py b/scripts/west_commands/run_common.py
index f40c64f..e85b714 100644
--- a/scripts/west_commands/run_common.py
+++ b/scripts/west_commands/run_common.py
@@ -356,8 +356,8 @@
 
         return None
 
-    def config(attr):
-        return getattr(args, attr, None) or yaml_config.get(attr)
+    def config(attr, default=None):
+        return getattr(args, attr, None) or yaml_config.get(attr, default)
 
     return RunnerConfig(build_dir,
                         yaml_config['board_dir'],
@@ -366,7 +366,7 @@
                         output_file('bin'),
                         config('gdb'),
                         config('openocd'),
-                        config('openocd_search'))
+                        config('openocd_search', []))
 
 def dump_traceback():
     # Save the current exception to a file and return its path.