switch test code for single_snp from log_delta to h2
switch test code for single_snp from log_delta to h2

MicrosoftGenomics/FaST-LMM,zhonghualiu/FaST-LMM,MicrosoftGenomics/FaST-LMM,MicrosoftGenomics/FaST-LMM,zhonghualiu/FaST-LMM,zhonghualiu/FaST-LMM