parallels: fix default options parsing

parallels block driver is completely broken since commit
    commit 75cdcd1553e74b5edc58aed23e3b2da8dabb1876
    Author: Markus Armbruster <armbru@redhat.com>
    Date:   Tue Feb 21 21:14:08 2017 +0100
    option: Fix checking of sizes for overflow and trailing crap
Right now even simple
    qemu-io -c "read 512 64k" 1.hds
ends up with
    Unexpected error in parse_option_size() at util/qemu-option.c:188:
    Parameter 'prealloc-size' expects a non-negative number below 2^64
    Aborted (core dumped)
The cure is simple - we should use 'M' as a suffix in default option value
instead of 'MiB'.

Signed-off-by: Edgar Kaziahmedov <edos@virtuozzo.mipt.ru>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Message-id: 1490002022-22653-1-git-send-email-den@openvz.org
CC: Markus Armbruster <armbru@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
