lalapps_MakeSFTDag: add 'getenv = True' to MakeSFTs sub file

-to fix zlib issue on ARCCA

@evan-goetz @keith-riles @gregory.mendell as 'getenv = True' is (in my experience at least) standard practice for most condor use cases anyway, and lalapps_MakeSFTDAG already uses it for the gw_data_find step, I'd assume this should be fine on other clusters/setups too, and I'll run a quick test on CIT too just to be sure. But please let me know if you remember any reason why this might have been conciously not included...?