Switch to 'mapped' access mode for hostfs

Passthrough mode only works as expected when running as root. On
Debian/Ubuntu systems qemu runs as user 'libvirt-qemu' and group 'kvm'
so all shared files must be chowned to grant access from guests.

Symlinks created on the host are still problematic because the Plan 9
filesystem has no direct notion of symbolic links, see [1].

[1] - http://ericvh.github.com/9p-rfc/rfc9p2000.u.html

testing/start-testing

@@ -19,8 +19,9 @@ check_commands virsh
 log_action "Deploying kernel $KERNEL"
 execute "ln -fs $KNLSRC $KNLTARGET"
 
-log_action "Deploying $ROOTIMGCOMPILEDIR as hostfs"
-execute "ln -Tfs $ROOTIMGCOMPILEDIR $HOSTFSTARGET"
+log_action "Deploying $SHAREDDIR as hostfs"
+execute "chown -R $KVMUSER:$KVMGROUP $SHAREDDIR" 0
+execute "ln -Tfs $SHAREDDIR $HOSTFSTARGET"
 
 for net in $NETWORKS
 do