Make the iwx(4) mac context task send its command only if we are still in

Make the iwx(4) mac context task send its command only if we are still in
RUN state when the task gets to run. Fixes fatal firmware errors where
mac context updates were erroneously sent in states other than RUN state.

Additionally, avoid scheduling a mac context task if a pending newstate
task is going to move us out of RUN state anyway.

Issue debugged by zxystd in OpenIntelWireless itlwm; patch by me.