Fix constructor coverage

[andre15silva]

Constructor coverage was broken by #35 . STAMP-project/test-runner#97 solves this.

See #35 (comment)

[andre15silva]

#81 partly fixes this issue. It now works for JUnit4 tests.

The following examples are still not recording the (empty) constructor execution:

Failed tests: testExampleFL12SpectrumBasedOchiaiDefaultMode(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<6> but was:<4>
testExampleFL6MixedSpectrumBasedOchiaiSpoonMode(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<5> but was:<4>
testExampleFL6MixedSpectrumBasedOchiaiDefaultModeManualTestConfig(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<6> but was:<4>
testExampleFL4JUnit5SpectrumBasedOchiaiSpoonMode(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<5> but was:<4>
testExampleFL5JUnit3SpectrumBasedOchiaiSpoonMode(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<5> but was:<4>
testExampleFL4JUnit5SpectrumBasedOchiaiDefaultModeManualTestConfig(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<6> but was:<4>
testExampleFL5JUnit3SpectrumBasedOchiaiDefaultMode(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<6> but was:<4>
testExampleFL6MixedSpectrumBasedOchiaiDefaultMode(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<6> but was:<4>
testExampleFL4JUnit5SpectrumBasedOchiaiDefaultMode(fr.spoonlabs.flacoco.api.FlacocoTest): expected:<6> but was:<4>