Btrfs: Fixup the code to merge during path walks

Add a bulk insert/remove test to random-test
Add the quick-test code back as another regression test

Signed-off-by: Chris Mason <chris.mason@oracle.com>

diff --cc fs/btrfs/Makefile
Simple merge

diff --cc fs/btrfs/ctree.c
Simple merge

diff --cc fs/btrfs/quick-test.c
Simple merge

diff --cc fs/btrfs/random-test.c
Simple merge