Enable integration tests

Enable integration tests

Due to overriding oparent's configuration in "build/plugins" section
it seems we disabled resolving dependencies and integration-tests couldn't
find junit-jupiter-engine on classpath (test files were found, however
@Test annotation did not mean anything to failsafe plugin).

- also moved plugins-management section lower in build-tree to
follow convention
- prelonged hvves-client-producer test certificates

Change-Id: Iaddd26735e489180eaa0153fdd1322f95bcff36a
Issue-ID: DCAEGEN2-1423
Signed-off-by: Filip Krzywka <filip.krzywka@nokia.com>