Resolve "Plot_time_domain_data and time of coalescence for waveform SEOBNRv4"

This MR fixes the correction of the epoch in time domain waveforms when using a segment duration that is not a power of two, e.g., SEOBNRv4 with 5s duration.

I don't think that this will impact O3 analyses, but I wanted to check. Bilby runs are just frequency domain, right? @christopher-berry @cjhaster @gregory.ashton

Closes #551 (closed)