qemu-img: Fix assert when mapping unaligned raw file
    
    Commit a290f085 exposed a latent bug in qemu-img map introduced
    during the conversion of block status to be byte-based.  Earlier in
    commit 5e344dd8, the internal interface get_block_status() switched
    to take byte-based parameters, but still called a sector-based
    block layer function; as such, rounding was added in the lone
    caller to obey the contract.  However, commit 237d78f8 changed
    get_block_status() to truly be byte-based, at which point rounding
    to sector boundaries can result in calling bdrv_block_status() with
    'bytes == 0' (a coding error) when the boundary between data and a
    hole falls mid-sector (true for the past-EOF implicit hole present
    in POSIX files).  Fix things by removing the rounding that is now
    no longer necessary.
    
    See also https://bugzilla.redhat.com/1589738
    
    Fixes: 237d78f8
    Reported-by: Dan Kenigsberg <danken@redhat.com>
    Reported-by: Nir Soffer <nsoffer@redhat.com>
    Reported-by: Maor Lipchuk <mlipchuk@redhat.com>
    CC: qemu-stable@nongnu.org
    Signed-off-by: Eric Blake <eblake@redhat.com>
    Signed-off-by: Kevin Wolf <kwolf@redhat.com>
    (cherry picked from commit e0b371ed5e2db079051139136fd0478728b6a58f)
    Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>