Bug 1934: Fix ready check

Changes to juju result in human readable output no longer
being applicable for the deployment completion check.
Changes to use json output instead.

Fixes Bug 1934

Change-Id: I65358c7f472956ed4238a5a61cceb1651d88feff
Signed-off-by: beierlm <mark.beierl@canonical.com>
(cherry picked from commit 67a3447f)