Fix LinearLayoutManagerPrepareForDropTest test names.

- Remove spaces from the config in BaseLinearLayoutManager.
- Add toString in SelectTargetChildren in LLMPFDT.

Test name goes from:
prepareForDropTest[Config{mStackFromEnd=true, mOrientation=0, mReverseLayout=true, mRecycleChildrenOnDetach=false, mItemCount=250, wrap=true}_android.support.v7.widget.LinearLayoutManagerPrepareForDropTest\$6@c7b61ef]
to:
prepareForDropTest[Config{mStackFromEnd=true,mOrientation=0,mReverseLayout=true,mRecycleChildrenOnDetach=false,mItemCount=250,wrap=true},selectTargetChildren:{0,1}]

Change-Id: I7fee1188e9c133f602797f7df97162d3569c79a4
2 files changed