Investigate using Maven Failsafe Plugin for integration tests

[sleberknight]

The project currently uses build-helper-maven-plugin to add the src/itest/java directory to the test sources during the Maven process-resources phase.

Since these are integration tests, perhaps it would be better to use the Maven Failsafe Plugin. In that case, maybe we could change so that Consul is started once for the entire suite of integration tests. Whether this makes sense will require more investigation, e.g. do some integration tests start Consul with different properties?