Fix device_block_size_fd to return bsize correctly incase of files.

This patch is for issue #287 (closed)

In the code for returning block size ( device_block_size_fd in lib/utils_device.c ), always returns zero in case of files and device_read_test is not executed.

This patch is to fix device_block_size_fd to return block size correctly incase of files.

Signed-off-by: Athira Rajeevatrajeev@linux.vnet.ibm.com