Fix constructor coverage

[andre15silva]

Constructor coverage was broken by #35 . https://github.com/STAMP-project/test-runner/issues/97 solves this.

See https://github.com/SpoonLabs/flacoco/pull/35#issuecomment-867639600

[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>