ivshmem-server: Don't overload POSIX shmem and file name

ivshmem-server: Don't overload POSIX shmem and file name

Option -m NAME is interpreted as directory name if we can statfs() it
and its on hugetlbfs.  Else it's interpreted as POSIX shared memory
object name.  This is nuts.

Always interpret -m as directory.  Create new -M for POSIX shared
memory.  Last of -m or -M wins.

Signed-off-by: Markus Armbruster <[email protected]>
Message-Id: <1458066895[email protected]>
Reviewed-by: Marc-André Lureau <[email protected]>