block: workaround for unaligned byte range in fallocate()

block: workaround for unaligned byte range in fallocate()

Revert the commit 118f99442d 'block/io.c: fix for the allocation failure'
and use better error handling for file systems that do not support
fallocate() for an unaligned byte range. Allow falling back to pwrite
in case fallocate() returns EINVAL.

Suggested-by: Kevin Wolf <[email protected]>
Suggested-by: Eric Blake <[email protected]>
Signed-off-by: Andrey Shinkevich <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Reviewed-by: Denis V. Lunev <[email protected]>
Message-Id: <1566913973[email protected]>
Signed-off-by: Eric Blake <[email protected]>