Make getting wifi state lockless.

Previous it was synchronized on the same lock that was held while
transitioning wifi states, effectively making it impossible to ever
find out about such states, and worse: making calls during transitions
block.

This manifested itself in a really laggy power control widget, which
I'm working on fixing in general in a separate change.

Change-Id: Ia34af98c73d7f5662e41360a213df87f6adaf130