test: fix DNS issue in test scenario

Doctor test was failed due to failure in resolving hostname at [1].

This patch replaces hostname by ip address, and also changes ssh route
from relaying instack VM to direct access from functest container to
the target compute host.

[1] https://build.opnfv.org/ci/view/functest/job/functest-apex-opnfv-jump-1-daily-brahmaputra/38/

Change-Id: I9d4f115cb43ec16540f7d9300d652625685477d5
Signed-off-by: Ryota MIBU <r-mibu@cq.jp.nec.com>
(cherry picked from commit 9171d14463ae1172a91125a49d8f8a53a36433e9)