Pin juju version to 2.8.1 and minor fixes in installer

Change-Id: Icc13bf72b664bad928d90e040f2ce55608dad759
Signed-off-by: David Garcia <david.garcia@canonical.com>
diff --git a/installers/charmed_install.sh b/installers/charmed_install.sh
index eb809d1..78a1e12 100755
--- a/installers/charmed_install.sh
+++ b/installers/charmed_install.sh
@@ -236,7 +236,7 @@
     ubuntu1604
     ssh-keygen -t rsa -N "" -f ~/.ssh/microstack
     microstack.openstack keypair create --public-key ~/.ssh/microstack.pub microstack
-    export OSM_HOSTNAME=`juju status --format yaml | yq r - applications.nbi-k8s.address`
+    export OSM_HOSTNAME=`juju status --format yaml | yq -r '.applications["nbi-k8s"].address'`
     osm vim-create --name microstack-site \
     --user admin \
     --password keystone \