Remove copy and leak of dex data.

To implement class redefinition we need to keep around a copy of the
initial redefinition. We moved this to be done in ArtClassDefinition
but left code that allocated and copied the buffer in RedefineClasses.
This code did nothing but leak memory.

Test: ./test.py --host
Change-Id: Ide5eafc7eda57eb5b1fc02eccb26091eacfae84f