Mark our own sphinx doc extensions as parallel read safe

This achieves a signficant speed-up in building our docs.

Change-Id: Ibc2b10cc9c3d4f447d011fbb7d91b09ba9eddc23
Signed-off-by: Clif Houck <me@clifhouck.com>

doc/source/_exts/automated_steps.py

@@ -193,3 +193,6 @@ class AutomatedStepsDirective(rst.Directive):
 def setup(app):
     app.add_directive('show-steps', AutomatedStepsDirective)
     _init_steps_by_driver()
+    return {
+        'parallel_read_safe': True,
+    }

doc/source/_exts/redfish_interop.py

@@ -184,4 +184,7 @@ def setup(app: Sphinx):
     app.connect('builder-inited', builder_inited)
     app.add_config_value('redfish_interop_source', None, 'env', [str])
     app.add_config_value('redfish_interop_output_dir', None, 'env', [str])
-    return {'version': __version__}
+    return {
+        'version': __version__,
+        'parallel_read_safe': True,
+    }