If the 9pfs mount tag is longer than MAX_TAG_LEN bytes, rather than
silently truncating the tag which will likely break the guest OS,
report an immediate error and exit QEMU
* hw/9pfs/virtio-9p-device.c: Report error & exit if mount tag is
too long
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>