project_fft_on_realX doesn't work as expected for FFTWPY

Created originally on Bitbucket by avmo (Ashwin Vishnu)

I found the forcing array generated by compute_forcingc_raw function to contain some complex values in (ky,kx)=(0,0),(0,kmax),(kmax,0),(kmax,kmax) rows and columns.

#!python

class RamdomSimplePseudoSpectral(NormalizedForcing):
    tag = 'random'

    def compute_forcingc_raw(self):
        """Random coarse forcing.

        To be called only with proc 0.
        """
        F_fft = self.oper_coarse.random_arrayK()
        self.oper_coarse.project_fft_on_realX(F_fft)
        F_fft[self.COND_NO_F] = 0.
        return F_fft

This was because project_fft_on_realX for FFTWPY returns the projected array and not operates on the same array. Correct me if I am wrong.

I replaced that with project_fft_on_realX_seq in operators_cy as a workaround.