[TRAVIS] change build matrix for OSX HDF5
[TRAVIS] change build matrix for OSX HDF5

- Due to https://github.com/CCPPETMR/SIRF-SuperBuild/issues/168, don't use SYSTEM HDF5.
- Try to use SYSTEM FFTW. We didn't have that in the matrix for OSX, and moreover it should reduce log size
to avoid hitting the 4MB Travis limit.

CCPPETMR/SIRF-SuperBuild,CCPPETMR/SIRF-SuperBuild