Drop uuid-runtime and add coreutils stage-package

* Drop uuid-runtime from openvswitch stage-packages as it doesn't appear to
  be required. On a related note, the snap currently requires the openvswitch
  Debian package to be installed, which has a dependency on uuid-runtime.

* Add coreutils stage-package to nova part to enable use of /bin/chmod.

Change-Id: If673f37b78e681af79e1de48c4542cc37e2f14ea

snapcraft.yaml

@@ -194,8 +194,6 @@ parts:
       - python-all
       - python-setuptools
       - python-six
-    stage-packages:
-      - uuid-runtime
     filesets:
       bin:
         - bin/ovs-*ctl
@@ -225,6 +223,7 @@ parts:
       - libxml2-dev
       - libxslt1-dev
     stage-packages:
+      - coreutils
       - qemu-utils
     install: |
       touch $SNAPCRAFT_PART_INSTALL/lib/python2.7/site-packages/paste/__init__.py