Server list info when waiting NS

Adds output of opentstack server list to the check for ns instance
so that way we can see if there is any mismatch between the state
of Openstack and the LCM.

Change-Id: I3c7a47b254c9ded037a8bbcc44d7b0f8e8e6d92a
Signed-off-by: beierlm <mark.beierl@canonical.com>