Build and load binder/ashmem kernel modules on service start

As both kernel modules are not part of the standard Ubuntu kernel we
need to build and load them at runtime. We bundle this together with
the container manager start and reuse the classic snap scripts to do
the actual build in a proper environment.

scripts/classic-reset

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+set -eu
+
+ROOT=$SNAP_COMMON/classic
+
+if [ "$(id -u)" != "0" ]; then
+    echo "needs to run as root"
+    exit 1
+fi
+
+for d in /home /run /proc /sys /dev /var/lib/extrausers /etc/sudoers /etc/sudoers.d /snappy; do
+  if mountpoint -q "$ROOT/$d"; then
+    umount "$ROOT/$d"
+  fi
+done
+
+# cleanup
+rm -rf $ROOT