Make class redefinition work with native methods on stack.

Previously we would crash if we tried to redefine a class with native
methods if it had any native frames on a stack. This happened when we
tried to create an obsolete method for the native method.

Since native methods cannot really become obsolete in the same way
that regular java ones can we simply do not make any obsolete methods
for these native methods.

Test: mma -j40 test-art-host
Change-Id: Ib677f73faae52627a478aa7cfe870c1f2c4fb503