FIX small bug in unit test and tuning lcov for unit test covergage

This is supposed to solve the following bug detected by Jenkins:

```
/var/develenv/jenkins/jobs/orion-develop-unittest/workspace/test/unittests/serviceRoutines/getContextEntityTypes_test.cpp:78: Failure
Value of: out.c_str()
  Actual: "<discoverContextAvailabilityResponse>
  <contextRegistrationResponseList>
    <contextRegistrationResponse>
      <contextRegistration>
        <entityIdList>
          <entityId type="TYPE_123" isPattern="false">
            <id></id>
          </entityId>
        </entityIdList>
        <providingApplication>http://kz.tid.es/abc</providingApplication>
      </contextRegistration>
    </contextRegistrationResponse>
  </contextRegistrationResponseList>
</discoverContextAvailabilityResponse>
"
Expected: expected.c_str()
Which is: "<discoverContextAvailabilityResponse>
  <errorCode>
    <code>404</code>
    <reasonPhrase>No context element registrations found</reasonPhrase>
  </errorCode>
</discoverContextAvailabilityResponse>
"
```

@kzangeli , it would be a good idea to do a `setupDatabase()` to clean-up database before starting each unit test involving database. I would create an issue about it.

I have also taken the opportunity to do a small fix in makefile coverage target for unit tests.