Fix unit tests when running from the command line on a fresh setup

[dangg]

Situation: According to the documentation at https://github.com/messagebird/java-rest-api/blob/master/README.md running the command

mvn test -Ptest -DmessageBirdAccessKey=[your access key] -DmessageBirdMSISDN=[your phone]

should run the tests, however the tests are skipped

The issue seems to come from the configuration under the default profile default <skipTests>false</skipTests>

Before changing this we need to ensure we don't break something else (such as builds)

[rvt]

Perhaps it makes sense to split the tests that require DmessageBirdAccessKey and DmessageBirdMSISDN and move these to integration tests. While leaving the pure unit tests in place.