As part of the CMake port we updated the duration formatting to contain
maximum of 6 decimal places but without trailing 0s. There was a bug
however where it used 6 significant digits rather than 6 decimal places
(`%g` rather than `%f`).
This fixes the bug and also updates the MPD sample files for the
integration tests to contain maximum of 6 decimal places.
The time for the previous segment was used when generating the segment
name. This resulted in the first segment being overwritten and
mismatching manifest and media files. It led to playback problems.
Issue #472.
Change-Id: Ia8130ce261585e1a2ede83b26de3e32508de087f