wrapcommand: allow adding additional arguments to commands
This allows eh.wrapcommand to specify additional parameters to be added to the
commands being wrapped. This will be useful when wrapping strip in the future.
pushexperiment: remove use of obsolete._enabled
pushexperiment.py was using obsolete._enabled but it didn't cause any tests to
fail so I didn't see it. Let's go ahead and replace it with the new
obsolete.isenabled() api.