Update juju_epc to leverage on new scenarios
It avoids duplicating codes across all OPNFV testcases.
It also fixes the issues when starting mongodb [1] by upgrading juju agent.
It stops supporting keystone v2 as the other testcases.
[1] https://build.opnfv.org/ci/view/functest/job/functest-compass-baremetal-daily-master/lastFailedBuild/console
Change-Id: I06cddddef1121292ffb695dcb73aa79a07c23192
Signed-off-by: Cédric Ollivier <cedric.ollivier@orange.com>
(cherry picked from commit
592584fbde2fb9b3b58015d374b2100026310d24)