BUG: Fix test error in scipy introduced by commit d8fd283.

Revert "ENH: ma.asarray() and ma.asanyarray() will pass through input
        of the correct type."

This reverts commit d8fd28389adb491e24b7cdc25cd1b20f539310c3.

That commit caused test errors in scipy, which was apparently
expecting a copy rather than a passed through array. The idea
may be good, but at a minimum it should probably be preceded
by a deprecation period.

Closes #4675.
Merge pull request #4677 from charris/revert-d8fd283

BUG: Fix test error in scipy introduced by commit d8fd283.