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/full_install_osm.sh b/installers/full_install_osm.sh
index eaf79d7..01a1bb2 100755
--- a/installers/full_install_osm.sh
+++ b/installers/full_install_osm.sh
@@ -1417,7 +1417,7 @@
      echo
      echo "1. Get the NBI IP with the following command:"
      echo
-     echo "juju status --format yaml | yq r - applications.nbi-k8s.address"
+     echo "juju status --format yaml | yq -r '.applications[\"nbi-k8s\"].address'"
      echo
      echo "2. Create the OSM_HOSTNAME environment variable with the NBI IP"
      echo