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/testing.conf

@@ -29,6 +29,8 @@ SWANVERSION=5.0.2dr4
 
 # Build directory where the guest kernel and images will be built
 BUILDDIR=$TESTDIR/build
+# Directory shared between host and guests
+SHAREDDIR=$BUILDDIR/shared
 
 # Logfile
 LOGFILE=$BUILDDIR/testing.log
@@ -52,12 +54,13 @@ BASEIMGMIRROR=http://cdn.debian.net/debian
 # The root image is the origin of all guest images. It is a clone of the base
 # image and contains additional test-specific software and patches.
 ROOTIMG=$IMGDIR/root.$IMGEXT
-ROOTIMGCOMPILEDIR=$BUILDDIR/compile
 
 # libvirt config
 NBDEV=/dev/nbd0
 NBDPARTITION=${NBDEV}p1
 VIRTIMGSTORE=/var/lib/libvirt/images
+KVMUSER=libvirt-qemu
+KVMGROUP=kvm
 
 # Directory where test results will be stored
 TESTRESULTSDIR=$TESTDIR/testresults