fiemap_writer: Add PinStatus check for fiemap writes.

Note that the check needs the kernel built with latest f2fs.

Bug: 122138114
Test: fiemap_writer_test /dev/block/sda21 \
      --gtest_filter=VerifyBlockWritesF2fs.CheckWrites

Change-Id: I0afbc14241f74ed368438a64afbdb97e3376f1f6
Signed-off-by: Sandeep Patil <sspatil@google.com>