The opening everybody's NOT talking about . . .
It's all been very hush-hush till now, but if all goes well, the lower level restrooms at the Museum of Fine Arts will be, well, "flush" with art by Boston artists right about now.With a wicked nod to desperate precedent - a famous "show" of contemporary art in the MFA men's room in 1971 (at left) - local artists will be sneaking in to install their own work in the spiffy latrines below the n…