[testing] adding member to check whether WVFPDP active

[GitPaean]

alternatively, we can use

    bool WVFPDP::active() const {
        return this->dp != 0.0 || this->m_fp != 1.0;
    }

[GitPaean]

jenkins build this opm-simulators=4958 please

[GitPaean]

alternatively, we can use

    bool WVFPDP::active() const {
        return this->dp != 0.0 || this->m_fp != 1.0;
    }

Using this way will be much less work and not need to think about how it should be affected by the RESTART implementation.

We can also explore usage of std::optional for this purpose.

[GitPaean]

jenkins build this opm-simulators=4958 please