The latest vhost-user changes changed the VHOST_SET_MEM_TABLE handling.
Now the memory regions are mapped from dev->mem. The BIOS is registered
at address 0xfffc0000 which is out of memory boundaries for guests with
less than 4G RAM. Calling qemu_get_ram_fd with this address causes abort()
in qemu_get_ram_block with "Bad ram offset".
To prevent this situation we introduce a new function to check if the address
maps to any RAMBlock - qemu_is_ram_block. This is used in VHOST_SET_MEM_TABLE
handling to revent the aborting call to qemu_get_ram_fd.
The related vhost-user qtest is also updated to reflect the changes in
vhost-user message structures.